So, I have a pretty Beefy computer. Rtx 2070 with a intel core i7-9700k and 16gb of Ram. But lets say when I run a clip, it runs fine. I split clips then run them it skips frames (Doesn't leave like 5th frame from ending the first clip) I can barely even run this at Quater quality.
Bump. On my machine it's even worse. Try to create proxies, and if you'll work with the proxies, preview will be fine. Preview set to "preview", not good or best, because then Vegas will use the original file instead of the proxy.
BTW your project is not 300p right?
What's the point of having 300p footage? Unless you want a frame perfect 1/5 slow motion in a 60p project , it's pure wasting resources.