Yeah I actually found the answer to my first question by searching just a bit in the modding board Dx
And I think it contains all we need :
Tutos
Tools (we actually don't need this, but it's interesting)
I'm a bit too lazy to start this right now but I'll read stuffs around and think about what to do precisely.
We can apprently tweak each joint max speed (the max speed it can reach) and each joint power (the time it takes to reach max speed)
We'll have to try that out !