#1 Yes, you could run any gauge you want I believe a 2AWG would support most amps. The thing is most ppl leave the OEM wires in place so the Big 3 wires are redundant. One word of caution I have for you is make sure you don’t go around the ground wire amp meter (maybe only for 04+ model GPs) or your computer will freak.

#2 Wire stripping…ah what? Dude seriously. All joking aside maybe you should get some help on this. And for crimping, the most affordable crimper is a “hammer crimp tool”.

#3 The difference I have noticed is definite increase in voltage/less voltage drop at idle with high electrical load. Off idle, no noticeable difference. Upgrading your wires only gets you a little bit more, you might need a HO alternator.

Good luck.