For reference my PC specs are i7 6700K, GTX 970, 16gb RAM, SSD, Win 10. I tested on a mod light build of
USSEP, textures for everything,
JK's Whiterun,
Waterplants,
Real Wildlife,
Birds of Skyrim,
Birds & Flocks SSE,
Populated Cities, Towns & Villages,
Immersive Citizens,
Vivid Weathers &
Rudy ENB.
Without this mod I have a near constant 60fps everywhere with a slight fluctuation of 1-2fps in places.
With this mod enabled you'll definately hear your fans rev up! There is a big drop (10fps) whilst stood at the entrance looking up the main street as well as on the top steps of Dragonsreach and looking back across the city. It soon sorts itself out though when you turn away. With Rudy ENB on I lost a couple more frames here and there but nothing to write home about.
These are the longest draw distances in the city and the only thing I can do is to delete some stuff or get a better PC, I'm happy to live with it! I have added more occlusion boxes where I can in order to help keep performance up.
The
Jk's Skyrim - Dawn of Skyrim Patch version will cause further framerate drops and is only recommended for those users with a beefy machine. Though it's definately still playable on my set up.
As I turned on the population and creature mods performance did decrease further by a few frames here and there but the game was still very playable. There will also be increased loading times simply because it's loading more assets.