With Shulk the only thing I feel like I can give advice on is edge guarding Shulk, which is highly useful in the MU. First lets look at the different recoveries, Without Monados his recover is poor in horizontal recovery reliant on his jump to get him horizontal distance, his airspeed is 24th (Without Monados all the statistics are for Shulk without Monados activated if that is different I will let you know) Actual up special used for recovery has 2 different strikes, the First is similar to the movement of Marth's Dolphin Slash (not in speed) This on if you are hit by it will launch you upwards, it is where he get most or hit vertical recover from in this move. The second strike is he faces forward (Relative to his previous position) and strikes making him rise a little extra in height. The second strike gives high horizontal knock back and if you are hit by it could easily turn into a stage spike. He can cancel the second hit allowing the oportunity for a mixup, if he does only the first hit it has the potential to auto snap. If he continues he will hang in the air for a second and will grab the ledge as the animation end. After his up special he is immediately put into bad recovery. His recovery does not have any invincibility frames, intangibility or protecting hitbox besides the sword. His recovery can also be enhanced by his jump manado giving him a larger jump other stat buffs and nerfs also occur but I will talk about that later. Pikachu's recover you should already be familiar with and as
Ninj4pikachu
said before that we outclass Shulk's recovery tremedously.
Now for how to actually edgeguard Shulk effectively,Pikachu has an amazing edgeguarding kit and I will go over each of them in turn and their uses against Shulks recovery. If you feel like I have missed something that is realistic to be used in Edgeuarding Shulk, let me know.
Nair- The sweetspot of nair has the most knockback of any of Pikachu's air moves and will knock shulk back the farthest or the strongest stage spike, however this moves has little range and the sweetspot does not last very many frames (3 frames) the move knocks you at about a 50-60 degree angle and Shulk could still make it back I prefer to use this out of shield against shulks ledge otpions than offstage.
Dair- This move permanently sweetspots with a high knock back hit, does not spike, the hitbox is underneath Pikachu so this could be usefull if you fastfall from above Shulk which could gimp him or stage spike you would also be very close to him I would not recomend this move for lack or range EXCEPT if you are coming from above this move if better for edge guarding at high percents
Bair- Dropdown back air is a popluar strategy for Pikachu since it carries the opponent possibly under the stage, knocks him away, or stage spikes, the opponent can DI the move to control the way they are knocked but take advantage of this, If they DI away from the stage, then move away from the stage so they are knocked as far away as possible, they DI in the move close or make your distance fromthe stage unpredictable so it is harder to get the tech. A dropdown bair can be stopped by Shulk's sword in the process and they can B turnaround towards to away from the stage making it almost a 50-50 whether you get hit by Shulk.
Thunder- Thunder has different properties on different stages and part of the move The top of the Bolt will spike you and drag you down in the bolt, If you hit just the actual bolt it will do mostly vertical knckback similar to roughly 75 degrees. The third stage is when the bolt hits Pikachu and causes Blue electricity to flash around him. This blue lightning hitbox is the most powerful of the 3 hitboxes and Pikachu has invunerability frames (34-44). The Dragdown hitbox usually combos into the contact hitbox because the opponent is dragged down with the bolt in the the blue electricity. This gives Pikachu to pluck shulk out of the air if he recovers high. Another use is immediately after a drop down bair Shulk with do a vertical recovery jump up and thunder to catch him drag him down and kill him. (either off the side if precents are right or gimp him). The contact hitbox alone is not really useful for edgeguarding in general it could be used if you are right next to the ledge for a 2 frame. The third hit box is the bolt itself and is extremely long lasting and will continue downwards for 16-85 frames, making this an excellent 2 framing tool. If you throw off and thunder and Pikachu's momentum is goinig away from the stage ESAM lists some followups in this video (Not for Shulk but in general but Shulk is mid tier in weight)
https://www.youtube.com/watch?v=Nmzl7AuyF0Y
U air- Not much to say other than it can combo into a Fair-Footstool
Fair- Fair is a very interesting move with a plethora of properties to use for edgeguarding the most flashy way to do this is a fair-footstool, which if carried out properly from ledge our you could IN THEORY get the footstool in the air without the grounded setup. If the fotstool is landed it could be fatal (not exactly useful but worth mentioning) Fair also has a drag down property similar to bair, allows a frame advantage to Pikachu (again not very useful to edgeguarding but possibly good to know) Fair is a deccent option for getting a stage spike, or at early percents (extended by shield mode) can combo into itself possibly fair chaining Shulk into a gimp. ESAM's video on a fair footstool
https://yt.eltuboadventista.com/watch?v=NVNJna7Qy0U
QA- Most of the uses of QA should already be known, however ESAM at one point SHINE 2016 he gimped M2K 2nd game with QA at extremely low percents not sure if applicable for Shulk but useful to know. Could if started near Shulk could take away Jump momentum.
Tjolt-There are 2 different forms of tjolt that should be established airbore tjolt and grounded tjolt
Grounded- This form of 2 jolt will climb up and down walls interfering with Shulk's recovery if he does a nearly vertical recovery also can be used to cover an aerial to ensure a safer approach.
Aerial- Use this defensively to make him lose Jump momentum and force him to recover low to allow for an easier edgeguard. I personal use this the most immediately after a forward or back throw offstage.
Ok now that we have covered the different tools used in Pikachu's edgeguarding lets go a bit more in depth on how this can be more applicable for Shulk.
Since Shulk does not have anything protecting him all Pikachu really has to worry about is if he will
recover high or low and
when he uses his DJ (double jump) and where his
Sword will hit
Recovering high: most useful tactic I have for when Shulks recover high is to go underneath them and try to snag a dragdown thunder ( try to be subtle with it and not commit and go really deep). If you get predictable then you need to bait out and airdodge and continue the punish. Try to use you DJ before using the thunder to allow extra height and help the chances you won't SD. If he tries to armor through you attempts with Backslash then just shield and punish by throwing him offstage or another kill confirm if available.
Recovering Low: Before we get into reactions for Shulk recovering low we should probably cover how to get him to recover low
A: Heavy pressure with possible dragdown thunder
B: A flurry of Thunder jolts
C: Punish his landings if he does not go for ledge
Ok so now you have the Shulk recovering low there are a plethora of options for this I will take this in 2 chunks one for safer methods and more agressive methods. However in either situation GET RID OF SHULK'S JUMP, it is very rare that he will not use his jump to recover (as long as he is knocked a deccent way from the stage. Getting rid of it should almost always be your first priority.
Defensive: Basically you don't really want to go offstage, you have a lead and you feel like you don't want to chance a reverse edgeguard, so you throw an array of projectiles to harras and kill Shulk. Thunder and Tjolt will be your main tools, if he reovers low jump and shoot tjolts to possibly take his jump and if he recovers high try to do a dragdown thunder (unless you mess it up really badly it should be safe) or wait and hit him with a thunder 2 frame or hit him before he snaps ledge so he does not get his DJ back. You are more then welcome to switch im=n between defensive and oiffensive you could start with tjolts and end with a bair or dair or start wih fairs and dairs and nairs and finish with a thunder 2 frame.
Offensive: Dropdown bairs and dairs are useful for knocking Shulk away and agressive aerials to take away his DJ and knock him farther into the blast zone, taking his jump is even more important when he is in his jump monado, he will also take a bit of extra damage. In the process you should be aware that at low percents you have little knockback and therefore very low chance of gimping or killing Shulk, however an edgeguard is not always meant to kill, racking up extra damage is important to Pikachu. at higher percents 70+ you should be aiming for a kill, without his jump monado activated his recovery is lamentable and you have a decent chance of scoring a gimp. Also test your opponent's teching ability, if he gets a tech reasonably often I would try to gimp him without a stage spike, if that is not working you can make him tech multiple times in one go. As I mentioned before Pikachu has a ton of different mopves with different multi hits and knockback qualities. If he techs then hit him again and again and again. Make it as hard as possible for him to keep track of what you are using and try to do multiple things every time because if he is gonna tech by golly we are gonna make it as hard as possible!
In summary I would like to say that edgeguarding is intersting in the fact that it is not set in stone, different people have different styles and methods for their edge guarding and these are my own methods and tips. Take what you want from this and use it
be creative.
PS. If you would like me to do something similar in the other matchup threads let me know and I will be constantly referencing this because a lot of this info is very general.
Sources: Krogane Hammer and ESAM's youtube channel