In the SPlat hip hop mix template, there's a mix bus that seems to do mastering.  This mix bus has two master fx chains:  Louder and Scooped, and Smooth, and it sends to a parallel compression bus.  Is it correct to assume that the export is both mixed and mastered and no further work needs to be done?  And is there some advantage to mastering like this, as opposed to exporting a mix file that then gets used in a mastering project?
 
Quinn
SONAR Platinum, Tascam UH-700, Sputnik, Windows 10

Hmmm. This is a tricky question because the answer can be yes or no depending on sound you are going for. Hip-hop ranges from live acoustic instruments, to sampled material from every genre to synth based EDM like sounds with lyrics. I'm sure that template works well on a particular subset after some tweaking. I think these templates are meant to give an idea and not necessarily meant to be a simple solution.

I personally prefer a separation of mixing and mastering processes. I also have gotten into habit of setting up multiple templates of my own depending on subgenre. My setup for a trap song is completely different than for boombap.

The simple answer is to try both ways and A/B your results. No answer is going to tell you more than your ears and/or the ears of others.