There are other threads about similar issues with similar cards.
Did you try to update the graphic driver to the latest from NVIDIA?
Are you on LR 6.6? Did you have these issues with 6.5.1 also?
If you have links to the other threads I'd love to look through them! And yes my lightroom and nvidia drivers are totally up to date, and it's always been sort of a problem but with this newest update it's way worse than it used to be! What's even weirder is that my dual core mbp is way faster with lightroom. I can thumb through photos and edit like a breeze, yet my way more powerful 12 thread desktop with a discrete gpu struggles.