“My main issue is the preview in multicam mode with a 4k track.
I decided to check performance again since I re-installed Vegas. Now I get full playback in ‘Preview’ but the CPU maxes at any ‘Good’ range and playback rate drops dramatically.
CPU upgrade would certainly help that, but in fairness ‘Preview’ is adequate to edit to.”
You may already know this …
I assume you are using proxy files for 4K …
Check out page 102 in the manual. Only draft and preview uses the proxy file, if you use good or best then you are using the 4K file alone for preview, obviously more difficult for your PC.