Hello,
I put a 1080p60fps iPhone SE video on Vegas Movie Studio 14 Platinum timeline, but when I editing it is very slow / lagging. I tried to make the preview to draft quality (quarter) and turned and enabled GPU too.
Plus the video a bit longer than audio, that cause audio desync from a point.
When I try to edit a GoPRO MP4 video, with same quality and resolution, no problem at all. Only I have this issue with .MOV files.
My comp: Ryzen 1200, Radeon R7 265, 8G RAM, 1TB SSHD