He's even said as much:

I throw the spaghetti against the wall, see if it sticks, see if it's al dente. I know the material, and then, of course I want to try it a bunch of different ways. Give the director so much to work with, so many levels of emotion, so many levels of cartoon. I'll do them all night if they let me.

To me that is him finding it so fun he just wants to try each part every which way he can and find what works, because he's truly enjoying trying it out because he wants to try it a bunch of different ways, not because he's being told to.

Not "I have a specific thought about how this works", or even "I know what the director needs from me", but "This is so fun I want to be wild with it and see what I can do!". Which to me is what makes Carrey awesome as Robotnik.

He absolutely has. I think that’s part of why we haven’t seen him in a ton of things in the last 15 or so years. I know he went through a phase where he primarily filled his time with painting, and he had a giant warehouse studio where he’d spend gobs of his time pouring himself into stretched canvass. Maybe this is just his next step…