Gem e825 changing tire/rim size

I currently have stock 10” wheels, and am looking into Putting 12” wheels on it.
Will I have to worry about it rubbing the rear fenders,? there does not seem to be much clearance.

Rim size doesn’t mean anything. Outside diameter of the tire, Tire width, and rim offset are the important factors. usually if you stay at 21 or 22 inches in diameter your ok.

Are the bolt patterns the same as a golf cart wheel?

An e825 is a 4 x 4" pattern, 0 offset. Some 4 x 100mm rims will fit, some won’t.

Newer model 4-bolt hub gems seem to have better luck with the 4 x 100 pattern.