I'm new and I have some questions on software

now my EFI a is Haswell, if I upgrade ONLY my gpu, I will need a Polaris 10/20 EFI?or I can't upgrade atall?
would I be able to upgrade systems? and do I need to download specific kexts for Polaris ?
can I just drag my kexts from the other EFI?
where can I find a Polaris 10/20 EFI? (can't find one)