1080p bro. I'm checking my temps and their not hitting more than 60. Either it's just the upgrade from 7 to Windows 10, which I think I should've done a clean install OR I believe it's a fault on Rockstar's part. Some are still getting problems with the game from the latest patch. New update should be coming out on Tuesday, so fingers crossed, it resolves the issue!
Well I'm sorry to say I can't relate to that. I upgraded to Windows 10, didn't do a clean install and GTA 5 actually runs a tiny bit better than it did on W8.1 with a combination of high/ultra settings with only one advanced setting engaged.
As suggested above you could try reinstalling your drivers.