The pie menu lag happens because your game is boggled with options on the pie menu, store content that adds gameplay does that, but if the lag stays under 1 sec it's not a huge issue. Just depends how you can personally deal with it. The turning around lag I get with too little texture memory, You may also want to turn a few options down even if your graphics card maybe able to do ultra. Turning down trees, visual effects & lighting to medium may drastically improve your performance while having very little effect on how the game looks.
Easiest way to make the game regonize your card & icrease texture memory is to download the progran "TS3 GPU Addon" from nexus mods, it will do it all for you with a few clicks.
The lag you get other than that, sounds like routing issues. If you have Nraas register installed, go into it's setting and animal control, and turn wild horses either completely off or down. I usually have them at 1 raccoon & deer, 3 stray cats & dogs and then 2 wild horses. Horses are very prone to routing failures. Also download the mod "Interractions on sloped terrain" from ModTheSims, that will clear a lot of routing failures.
