I got decent sharpness with red Pico 4 with the following main settings although this was with a RTX4090. When I had my RTX3090, I needed to run things lower.
Pico 4:
90Hz
MSFS:
High quality preset
TAA mode @ 100%
Sharpness 0
OXRTK:
Fixed Foveated Rendering - Quality preset
CAS Sharpening @ 40%
Override resolution 4120x4120 per eye
Virtual Desktop:
VDXR runtime
HEVC 10 bit codec
Bitrate 150Mbps
Sharpening @ 70%
SSW disabled
With the RTX3090, from memory I had the following:
Pico 4:
72Hz
MSFS:
High quality preset
TAA mode @ 100%
Sharpness 0
OXRTK:
Fixed Foveated Rendering - Quality preset
CAS Sharpening @ 40%
Override resolution 4120x4120 per eye
Virtual Desktop:
VDXR runtime
HEVC 10 bit codec
Bitrate 150Mbps
Sharpening @ 70%
SSW Enabled
The biggest changes were 72Hz and SSW enabled for the RTX3090. After that, you can play with DLSS instead of TAA mode in MSFS and also look to lower the override resolution in OXRTK to 4000x4000 or lower but definitely do not go below 3120x3120 per eye as this setting has a big impact on actual resolution resolved in the headset. Also avoid over sharpening - I recommend disabling this in MSFS and use in Virtual Desktop or perhaps add a bit in OXRTK as I have. Overdo this and it will have a negative impact on visual clarity.