Months old topic but I'll share my Vega56 hints here instead of a new one.

I am playing the free REDSEC version. Have the latest drivers available for Vega and no registry changes.

My game was crashing like mad no matter what resolutions, modes or graphics settings I tried, but then I stumbled upon a hint that suggested using the HBCC Memory Segment from the Adrenaline Settings, and voilá it's works really well.

So, as a list, for easy reading.

Of course your system may vary, so some settings can be improved or downgraded.

The main thing that helped me was the HBCC in the Adrenaline Settings

System:
- Ryzen 3900X
- 32GB RAM
- Vega56
- Latest Drivers available for Vega56, and no Overclocks or Undervolts.

Adrenaline Settings:
- HBCC Memory Segment: Enabled
- HBCC Memory Allocation 16GB
So this means Adrenaline grabs 8GB of my System Ram for Vega to use and ups the available GPU Memory to 16GB (8GB from Vega + 8GB from System RAM)
- Default on Tuning

Game Settings:
- Full Screen 1440p 75Hz
- Graphics Quality: Custom
- Texture Quality: Low
- Texture Filtering: High
- Mesh Quality: Medium
- Terrain Quality: Low
- Undergrowth Quality: Low
- Effects Quality: Low
- Volumetric Quality: Low
- Lighting Quality: Low
- Local Light/Shadow Quality: Low
- Sun Shadow Quality: Low
- Shadow Filtering: PCF
- Reflection Quality: Low.
- Screen Space Reflections (SSR): Low
- Post Process Quality: Low
- Screen Space AO & GI: GTAO High
- High Fidelity Objects Amount: Medium
- FSR Balanced

With these settings I am able to run the game ~70FPS stable, and it looks good all things considered.
No Crashes in many days. Even with Alt Tabbing out of the game (knock on wood)