Ok I am glad I am not the only one - I have similar to everyone else (i9 9900k@ 5ghz, 64 gigs ram, RTX 2080Ti and the reverb).
for whatever reason my FPS Range is stuck between 20-40... and I haven't done a thing other than update drivers and the program. Before I was 40-45, but now im 30ish-35. Everything to lowest - max of 40-45 again... its really frustrating me, but I am glad I am not alone!