I just looked into your old thread, the CPU shouldn't bottleneck the GPU,
You could try flashing bios again, but this time with the forceflash command,
For example: amdvbflash.exe -p -fa -fp 0 Sapphire.RX5700XT.8192.190905_2.rom
Try this vBIOS: https://www.techpowerup.com/vgabios/214469/sapphire-rx5700xt-8192-190905-2
Follow this guide: https://www.techpowerup.com/forums/threads/amd-ati-flash-command-line-cmd-syntax-mini-guide-windows.291671/
I would stick to the Nvidia card purely for the features and encoders. As well as a laundry list of other great features. As before mentioned by other users, you are giving up a lot for a small increase in performance. Not worth it. Glhf