I usually play KSP when my friend is here so I guess he's a nerd or something but he always counts my deaths and I have no idea why and only because Jeb is the main kerb
Well what mods are you looking for? Ex: Graphic mods, parts mods, etc
But if you're new to KSP I do recommend that you play through and understand how to this and that before mods because.. Good reasons
There's mods that aren't compatible like BD armory as Jas0n says, go around and check your mods to see if they're compatible or just remove all your mods, either works.
I usually set everything around low-medium where I get usually 15 fps, so I'm good for now but thanks. And I'm horrible at building ships with a large part count.