honestly jealous, tried to get this type of movement down a few times but never get the collision detection right.
Viewing post in Bel & Poppy
All I can say is that it takes a lot of fiddling...
Regarding platformer game feel (and collision code specifically), I've learned a ton from Zack Bell's website:
Understanding Collision Basics - Part 1
Understanding Collision Basics - Part 2
Sadly, the open source code for his excellent game INK is no longer available as far as I know.
In any case, getting collision detection right is definitely important. Once the basic engine is up and running, it's a matter of tuning player acceleration, jump height, air control, gravity and friction by trial and error until it feels right for the game.
The only real advice I can give is to adjust one thing at a time. If you look at my first gif, the character couldn't even jump yet, because I wanted to tune the ground acceleration and friction before adding any vertical movement. Same goes for everything else -- don't add double jumps or wall jumps until regular jumps are solid, and so on.
Hope that helps!