I just upgraded to V22. What is Latest Best Qual Render Settings for video to be uploaded to YouTube at highest quality. I am trying a "Magix" mp4 1080p render right now. a 5:15 timeline was 458MB
Is your source footage greater than 1080p? If so render to that resolution. If not test rendering to 1440p to see if YouTube gives a better codec and quality.
Not sure it matters whether you choose HEVC or AVC as it all gets reencoded. I'd avoid AV1 output from VEGAS due to frequent glitched frames.
I don't have Vegas 22, so one would need to download the trial versions and connectors marked for 22; I don't know if those have been released yet, but it is a good third-party product.