Nair will either combo Olimar to hell and back at lower percentages, or will generally put him in a very awkward position at higher percentages. His physics just totally fit the move, you know the way you CAN'T nair > grab Falco when he's at 0%? Well, against Olimar you can do that and more. Nair > nair > fsmash, nair > nair > fair > ledge- or edgeguard, nair > jab > grab, ENDLESS AND ENDLESS POSSIBILITIES depending on percentages, you can really knock yourself out on that one.
Aside of how badly his mechanics (his light weight and general floatiness) are, the move is rather safe in general. On shield, it's obviously extremely safe, the first hitbox beats most (not all) of his pikmin moves, if you keep timing it well you can give Olimar a hard time beating it through conventional means.
At higher percentages, its awkward knockback angle can screw him up as well.
Its speed makes it preferable over dair in close combat situations, you definitely can't use it as a long range approach (lol nothing works as a long range approach against Olimar), but its normal uses (decently safe, comboability, speed) are amplified in this MU because of the way Olimar works.
Do know that if Olimar is in the air, you should never fear him. Most of you probably already know this, but for the few who still actually play really safe when he's up there: don't. Every aerial you hit while he's in the air puts him in an even more awkward position, your air game beats his because of the STUPID aspect of his air game that's called priority. All of his aerials can be outprioritized. Of course we don't outrange him, but so long as you time everything well (it's a perfectly human thing to do) you'll beat him regardless. Your fair will beat his, your dair will beat his uair, your uair beats his dair, SO LONG AS YOU TIME IT WELL.
Know when you have to commit to using uair to remove pikmin. When they're on certain parts of your body, you CAN'T KILL THEM WITH NAIR OR DAIR DON'T EVEN BOTHER, I'd note exact spots but I usually do it instinctively lol sorry ^^. I hate it when I see Wario players using nair like 5 times to knock off 2 white pikmin, which'll do their 500000% anyway. I know it's a ***** to have uair go stale, but it's better than taking unnecessary damage.
Tires are not really good against Olimar, watch Krys' vids against Hilt (I believe it was Hilt), Pikmin are way more expendable and practically beat them out.
Standing on a platform is never safe, usmash usmash usmash usmash and there's nothing you can do. You can, in fact, even just get pushed off and the greedy ******* can go for another safe usmash.
You can go for dropzone fairs, they're safe so long as you recover by biking AWAY from the stage, and then DJing back to either the ledge or onstage itself (whichever one seems more safe). Watch out for dem purple pikmin though, they'll knock you off your bike
Bike works decently as a ledgeguard, but as I said earlier: the tires are rubbish. More often than not, you're wasting time pulling out your bike.
That's all for now, more later perhaps.