So to clarify, it is the windows 11 that is making problem, not the hardware right? İf i go with windows 10 there will be no problem because it is not hardware related? Sorry but the last time i built a pc was 2015, so i am far behind to understand some things clearly. So i am asking very basic. İ was far from computer hardware world for a long time.
I'm like you, haven't built since Ivybridge so just guessing on this new stuff.
My general rule of thumb is to match hardware and software within their own generation, give or take.
Best example of this was a Senior Center who's previous tech "upgraded" all the old computers to XP but the computers didn't have the memory for XP so they took an hour to boot because the were constantly hitting the hard drives after running out of RAM. The systems became essentially useless even though XP was "better".
Same thing applies these days. If the hardware and software are seriously mismatched there are bound to be compatibility/driver issues.
Getting back to your situation, AFAIK, your 12th gen CPU requires an updated scheduler to handle the 2 different types of cores ( performance and efficiency). Said scheduler is only available in W11 and is not in W10. So you "need" W11 for your CPU to work properly.
Your old 970 might be just fine with W11 but it might not according to the one reviewer on Amazon. I'd hate to see you buy a new system only to have trouble with it so I'm advising getting a CPU with integrated graphics as an insurance policy in case you have trouble with your old card. They don't cost that much more, cheep insurance against a possible problem.