First of all, welcome to smashboards!
As far as movement options are concerned in Ultimate, there are options such as being able to do any attacking option out of a dash (New), There is also a pseudo-dash dance like in Super Smash Bros. Melee, and also like in Melee, we have directional air dodging in additional to neutral air dodging, but understanding how these work stress where you are fundamentally as a player. The basic options, like being able to short hop are essential when it comes to combos, approaches and zoning, but a concept like “Tamohawking” which is the use of an “empty” short jump (basically, a short hop without commiting to an attack or any other option) is an advanced concept meant to force a reaction out of your opponent by or trick them. If I can compare it to a traditional fighting mechanic, it would be akin to doing an empty jump on wake up to bait or set up an ambiguous cross up.
The three movement options I previously mentioned are probably the most important, but check out concepts for movement in Melee like ledge dashing. Check out Advanced How to Play Melee part 1 and 2. There is some information that you could omit from the video, such as how to L-Cancel and Jump Cancel Grab, which are no longer in the game, but it breaks down howto use your basic movement options and concepts. I’ll see if I can find any more video recommendations. The Beefy Smash Dudes have really solid videos on specifics in Smash 4 and it’s mechsbics, and since Smash 4 is the closest I’m functioning to Ultimate, information there may be helpful.
Also, as far as defense goes, try to study the new perfect shielding mechanic, which requires you to release your shield at the moment an attack hits your shield to execute a parry. It’s very flashy, and gives you a solid frame advantage. It can be compared almost to Street Fighter III: Third Strike’s Larry mechanic, but it can’t be done in the air. Conceptually, the act of surrendering your defense to counter an attack is similar to 3rd Strike and Street Fighter Alpha. Similarly to Street Fighter, you can tech grabs with your own grab input, and you cannot walk or run past an opponent, so implementing some of your baser instincts from fighting games may contribute wholly to your ability to play Ultimate.
If there’s any more information out there I’ll let you know. Check the game pre-release section for more information about gameplay specifics as well. Good luck, and have fun!