For the reflections, please vote here: https://forums.flightsimulator.com/t/bug-reflections-broken-in-vr-since-update-5/
Putting shadows on Ultra didn’t do anything for me btw (Using the Fjord landing challenge as baseline)
For the shimmering, vote here: https://forums.flightsimulator.com/t/aa-downgrade-since-su5-in-game-not-menus-overlays/