2D Workflow Questions

Hi all, Looking for some answers from the 2D designers in Unty.

I´m looking in to a 2d Framework/ workflow to build my first game/ app. A 2d top down, hack and slash.
I´m planning on following some tutorial, like city evac or moon lander. Hopefully the tutorial will take care of most of the hiccups allowing me to focus on learning to import assets to Unity and make them look and behave how I want.

I´v build a simple walking animation, (6 sprite sheets): character, hat, shadow, character without sword, sword. There are 24 frames on each sprite sheet.
I intend to have 3 or 4 sprites on top of each other to represent the player character:
The Hat, would be used so I can change the color/ shader (representing different states etc); the character + weapon; and the shadow (not sure about using the shadow as I would have to make at list 8 different ones...but would like to test anyway)



I´m using TexturePacker, so my first question is if any of the 2d Frameworks available can use this sprite sheets, or must they be built inside the application (with individual sprites) ?
If the latter, can sprite sheets be exported ( so colors / transparencies can be changed, per sheet and not per sprite)?
Do they read the PNG transparencies or alphas must be provided?

Are the colliders generated automatically per sprite, and then follow the animation (hoping)?
With this in mind I can then mix different colliders: build the colliders using the animation for my character without swords (fig4) then generate one for the swords (fig5) them put them together on my character (fig1) (planing to use only simple colliders like cubes and cylinders)



And last, wish 2d Framework would serve me best to build this level/ image (fig 6, 7); Layer 1 background, L2 environment shadow, L3 small props, L4 character shadow, L5 character+weapon (+effects), L6 hat, L7 big props shadow, L8 big props..,
Sorry for the long post, hopefully the answers will help more users than myself.