Long time since I used Vegas. It has an extremely streamlined workflow, but for heavy files and projects, its engine is too weak (in my experience).
I suggest you try some other software.
I don't know if Vegas supports DNG sequences. But if possible in Vegas, then you will need to render the DNG sequence to Prores or DNxHD (both formats are very suitible for colour grading etc.) But they also seem to me as heavy formats for Vegas.
If you want a very quick and easy workflow, then render to mp4 at the loss of quality.
My last Vegas version I used was Vegas 10, many things might have changed since then. Maybe someone else here knows.