The scores I was originally getting seem on par with scores I've seen for similar builds in that 'other' well known forum.

My wife's PC steadily scores between 20.5 - 21.0k on 4k windowed max settings, and she has a 1080, not a 2080. We have similar PCs. She had the issue, too, for a day, scores dropped down into the 7000-8000 range, and then they just jumped back up with no apparent explanation.

I can still score 21k + in 1080p, I never even bothered running 1080p until after this issue cropped up.