L1-

check power outlet that your Power supply was plugged into, see it is giving power. Check and reseat all the power cables from your PSU

pretty most of high end gpus will have coil whine, Id suggest just mute the sound inside your brain LOL jokes aside, maybe try to put the pc further away?

Can you default your bios settings? To be this is more of a software issue

LIke what @fuzz0rsaid above, 86C isnt really a serious problem for GPU If you are feeling uncomfortable with a 86C GPU, you can position the front intake right against the GPU, and slightly increase the rear fan rpm(and top exhaust if its possible for you). Heat could be trapped inside your case because of the lack of airflow. Another possible solution is to clean dust on your GPU, might also solve the problem

at this point I recommend check your HIGHEST gpu temp after playing games for couple hours. Hot air might be trapped inside your case, thus high temp forced gpu to downclock

Check your nvidia control panel (assuming you are using a nvidia card), restore 3d settings for global, check if you turned on vsync or simply any sync by accident in games setting

I think you need to switch the input option from HDMI to DP on your monitor manually, have you done that? Video output should not be affected by motherboard bios, not to my knowledge.

@Natty Ice has given you the answer, Brand isnt the decisive factor to determine if a motherboard is good, you can refer to this list: for 5600x I personally would not go with x570 simply because it is somewhat a waste, a B550 Motar or B550 Tomahawk is pretty good in terms of pricing and performance

Prices for hardwares vary from area to area, but about 500 pounds you option is pretty limited. Maybe a 1060 super with i5 10400 or r5 3600, get an okay motherboard and cheap 16gb rams. If you have some extra money to spend maybe also get a larger size ssd.

so you disabled pbo ... and you have a 5900x .... Should have gotten a 10900k instead tbh...

I had 7700k and 10700k running warzone, its only cpu intensive while having 100+ frames 1060 is decent but not great, though sub 60fps is abnormal. The GPU usage in windows is often inaccurate you might wanna check it in GPUz while gaming check your warzone settings too some settings are crazy GPU intensive

Ahh thanks for the info, from what you had in the event viewer, I tend to believe that this is just a software issue. By any chance you have a spare pc to test the 2080ti on ?

I dont think so sounds weird, have you done any benchmark? CPUz Cinebench?

Thinking he is talking about the PSU VGA slot?

Have you tried to put your old 5700xt back in the prebuilt to see if it still crashes? If it does, its likely to be an incompatible driver issue If not, try to reinstall windows with only the 3060ti