The common denominator in your issues would be your PC. If games are working according to protonDB and you’re unable to get them to work on multiple distros that suggests its your PC.

There are two candidates in your specs - your RAM and your Graphics card.

As others have said, asymmetric RAM is unusual and it certainly was warned against in the past as it caused system issues. While OS may be much better at managing RAM bow, that doesn’t mean all scenarios can tolerate it. Given what Proton is doing is complex (running Wine, which is essentially a windows layer) I would not be surprised if the memory configuration is just a step too far - you have windows software using a windows compatibility layer for memory asking a linux is for memory access.

An obvious way to test this is to remove the 16gb stick from your machine and see what happens.

The other side is your graphics card - are you using the latest nvidia drivers?