These are some steps you can take to troubleshoot the issue with your RX 6700:Eliminate Hardware Issues:
Test with Stock Settings: Run your system with the GPU at stock settings (no overclocking or undervolting) for a few days. If the crashes persist, it might not be related to tuning.
Stress Test: Use stability testing tools like FurMark or Heaven Benchmark to stress your GPU under heavy load. If it crashes during these tests, even at stock settings, it could indicate a hardware problem with the GPU itself.
PSU Check: While you've upgraded your PSU, it's still worth double-checking its connections and ensuring it's functioning correctly. You can use online calculators to estimate your system's power draw and confirm if the PSU is sufficient.
Software Troubleshooting:
Clean Driver Install: Use Display Driver Uninstaller (DDU) to remove all traces of previous GPU drivers before installing the latest stable driver from AMD's website. Avoid modded drivers as they can be unstable.
Disable Overlays: Overlays from applications like Discord, GeForce Experience, or even Windows Game Bar can sometimes interfere with drivers. Try disabling them temporarily to see if it helps.
Repair System Files: Use the System File Checker (SFC) tool to scan and repair any corrupted system files that might be causing issues.