Place the 4K clips on the Vegas Pro timeline and go from there, yeah, that’s best advisable.
And you go about your edits as you normally would with any other HD or SD format, as long as
you have a powerful system.
There is no need for any 3rd party converters, and even Vegas itself can be used as a converter.
Steve Rhoden (Cow Leader)
Film Maker & VFX Artist.
Owner of Filmex Creative Media.
Samples of my Work and Company can be seen here:
https://www.facebook.com/FilmexCreativeMedia