You don’t need to use offload mode for vsync, just the amdgpu driver instead of modesetting. You should just clean up your config files as this seems a bit messy.
Besides /etc/X11/xorg.conf.d/90-nvidia.conf you also have /etc/X11/xorg.conf.d/20-amdgpu.conf defining explicit “Section Device”. You can delete both and instead use /etc/X11/xorg.conf.d/10-nvidia-primary.conf
Section "OutputClass"
Identifier "nvidia-primary"
MatchDriver "nvidia-drm"
Driver "nvidia"
Option "PrimaryGpu" "yes"
EndSection
you can then use the primarygpu option to toggle between offload and primary mode.