Funnily enough, that's exactly why I don't use cockpit view. I have no idea where the car is because of the lack of depth perception. In wheels view at least I have the wheels to use as markers to more easily judge distances. I find drafting behind someone in cockpit view almost impossible since I never know when to pull out and overtake. Could be I just need to get familiar with it, but right now I just can't do it.
You should have a FPS number in the top left of your screen when playing, if it goes below say around 15 and things start to stutter you see it for yourself!
You can't really take a screen shot of it as you need to see it in motion.
Yes it goes Jerky, the more cars on screen and at South City the FPS will drop, you'll get high FPS when it's just you racing. You don't really need to see it, you'll know when you get it because of the very low FPS and stuttering/jerky play.
I dunno if you have tried the new patch but with a server full of 28 cars, plus flying tires my PC starts to plead for mercy I've not tried 20 AI's but I imagine it would be worse.
If you want to see what your computer can do with LFS try the patch on a full server, starting from the back and going into T1.
W10 is a test patch. I think it's a safe bet that none of the league servers will install a patch until it's final and released to the public. So, if you install W10 you likely won't be able to connect to the STCC servers (though I haven't verified this).
Make a new folder (call it LFS2 or something) copy your original install into it and patch it up to W10...then you can have both, so there's no need to miss out in STCC etc, but you can play about with the new features.