Like do you move faster while crouching, move slower while jumping/tricking, things like that? It’s hard to tell from watching replays and it would probably be useful to have it written down for new folks passing by.
Was this something discussed in the Discord (which isn’t accessible at time of writing).

Hold down A/crouch for about 4 seconds and release it for a speed boost.

Interesting, is there a way to tell you’ve done it right? Something to help learn the timings.
Looking at some videos it seems to be around 2 seconds, maybe slightly less.

Yes. Your character will shout, as if you were doing a trick.
It's about 2 seconds. You'll get a feel for it after time.

Aside from that, there really aren't that many tricks or techniques to learn.
I'll list a couple of things that come to mind though:

Banking (Control stick diagonally down) helps with cornering.
You keep your momentum in mid-air so you don't lose as much speed as on the ground.
Tricks don't slow you down, but you can't control your character mid jump when and after you do them (even just grabs lock you in your movement). That's why it's discouraged to perform them outside of farming money in Any% or 100% runs.

Also, Tommy /w Star Board is commonly accepted as the fastest 'setup'.

hope this helps!

For full-game runs I guess there are some advanced techniques like keeping track of which weapons/items the opponents have and taking advantage of that. After a while you will notice specific places where you are likely get attacked. Also you can hear sounds when items are used if you listen closely. You should be able to deflect attacks as well by doing a grab just when the attack is about to hit you which is a lot easier said than done (jumping over the attack is simpler).