Replying to Video editing problems

So im trying to make a little season edit of some sort...
in the editor (sony vegas pro 12) i have a few different types of videos, i got vids from a dslr, gopro, iphone 5s, and vhs. My only problem is that the iphone videos are very shitty, there pretty choppy or laggy or something. is there any way i can fix this? im not very good at video editing. Also, what do i use for rendering settings? since i have videos from a vhs, i cant do anthing over 480p right? +k