TL;DR:
Try using SteamVR Beta 1.27.5 until Valve releases a true fix. Turning off OpenVR in Varjo Base will restore MSFS performance but will cause SteamVR to throw errors sporadically that will sometimes cause MSFS to CTD.
Details:
While turning off OpenVR in Varjo Base does indeed restore MSFS performance to pre SteamVR 2.2.3 levels - it’s not all roses.
SteamVR is not happy with OpenVR disabled in Varjo Base and it will throw errors that will (sometimes) cause MSFS to crash to desktop - this can even occur mid flight.
Alternate suggested workaround - run SteamVR “Beta” 1.27.5. Hopefully Valve doesn’t remove this option until after they truly fix the disaster that is SteamVR 2.2.3+.
You can opt in to this older version by going to Steam > Library > SteamVR > Properties > Betas > temp_v1.27.5 - Temporary branch version 1.27.5 (for testing).
Allow the version 1.27.5 beta to download then restart your system. You should see the beta version (and several other Steam VR betas) in your Steam library once you have successfully reverted.
You can now re-enable OpenVR in Varjo Base and everything should perform like it did before SteamVR 2.2.3 without the stability issues associated with disabling OpenVR in Varjo Base.
Note1: Recommend checking your Steam library each flight session to ensure it’s still on the old beta - there’s no telling when/if Valve will remove this old beta and force you back onto 2.2.3+. If that should occur, then disabling OpenVR in Varjo base might be the only viable solution left.
Note2: the community is reporting the newly released SteamVR 2.2.4 exhibits the same horrible MSFS performance with Varjo headsets as SteamVR 2.2.3.
The Steam bug reporting forum for this issue is linked below. Please drop them a line so they know this is a widespread issue that needs immediate attention.
SteamVR 2.2.3 Stuttering in DCS with :: SteamVR Bug Reports (steamcommunity.com)