I have doubts you would see any performance increases, and if you change your hardware you'll be in for a tough time but it would be a fun learning experience!
Thats a question I have. I have two laptops, a shitty amd ryzen thinkpad t495 and a fancy soon-to-be-corebooted Clevo NV41MZ with i7-11** cpu. Pretty crazy performance difference although the chassis and keyboard suck. But if I get the keyboard I want to simply swap drives, as there is nothing fancy, this should just work right?
Swapping CPU manufacturers entirely? I'd just start my kernel config fresh. Pull up the old one next to a new (default ) one and go down line by line. Odds are there are at most a few flags that would need to be changed, but it's a good chance to reevaluate your previous decisions too.
This used to be the norm, not a weird thing that noone has thought of before. If you do this your kernel will be a lot smaller, boot faster, and be a bit more secure. Once you're booted it won't make any meaningful speed difference though.
It makes a HUGE difference in compile time. Which only matters if you're building your own kernel anyway. It's a solution for its own problem.
I think it's a good learning experience though. There is genuinely a lot of stuff in there that you can easily, safely remove, and reading up on all the less obvious flags is fun.