Celia Alexis Wagar's CritPoints

Do you have any advice for a smash player that wants to get into 2d fighters (especially stretch fighter 5) I’ve never played 2d fighter but I am thinking about trying it. Also what controller should I get for playing on pc

Only the same advice I have for players trying to get into traditional fighting games in the first place.
https://critpoints.wordpress.com/2015/03/20/street-fighting-for-beginners/
This links to a TON of other guides at the bottom. Please consult all of them, and the shoryuken wiki page for the particular fighting game you want to play.

What I’ll say is, the control system will not feel natural to you at first. You have access to more moves at a time, and it’s not going to be as obvious how all of them are used, because they all point in the same direction and they all come out and recover much faster. Learning what each of your normals is good for, getting them all down to the point where you know which one of them hits in which place at which range on command, and being able to identify what a normal is good for on a character you’ve never played before.

Practice anti-airing jump-ins. A great training technique is to record the bot doing something you want to practice against, like jumping in with a medium kick. A good thing to do is have the bot jab twice beforehand so you can react to the timing and simulate reading the move. Learn to use both normal anti-airs and special anti-airs. normals are good for reacting when you’re uncertain when they’ll jump, specials are good for reading, when you’re certain they’ll jump and when. You need both of these, you need to be fast and accurate at both of these.

Get down blocking. Blocking is absolutely critical, a lot of beginners don’t block enough. Block low all the time, then high when they’re in the air or doing an overhead attack. You can’t react to lows, but you can react to the other two, and lows deal more damage. As you get better, learn to fight standing up moving back and forth instead of being rooted to the ground in a blocking stance. Learn to do the block motion while jumping in, while attacking, while dashing, so you always do it the first instant after you stop. This will help you play charge characters too.

Learn what frame advantage/disadvantage is and how to identify which moves have it. Or look up framedata until you get the pattern. Learn when moves hit, how long they take to recover, etc.

You can use whatever controller you want. All major fight sticks have PC drivers. There are PS3 and PS4 drivers and wrappers to make them behave like 360 controllers (which is what most things on PC support). For 2d fighters the control choice doesn’t matter a great amount unless you plan to switch at some point.

Oh, and play a lot of people.