Fermenting under pressure allows for faster turn around and warmer fermentation without off flavors. The fastest I've done with this method from grain to glass is 10 days for an average gravity (~1.050). There's a brewer on HBT that does lagers at room temperature very quickly. My process is:
Day 1: BIAB/No-chill in corny
Day 2: Pitch yeast, attach blowoff tube to gas qd.
Day 5: Pull the gas qd, "capping the fermentor"
Day 10: Fermentation complete, and fully carbed, ready to transfer to serving corny
It definitely helps clarity to cold crash for a day and close transfer to the serving keg on day 11-12. I have also experimented with serving from the fermentor (from no-chill to serving all in the same vessel). It definitely works, but I pulled a lot of trub at first, and then a few oz on the first glass for about 3 days, so unless you don't mind dumping the first little bit it's worth it to transfer.
With the above method I've been running my entire homebrew operation with 3 corny kegs. I'm the only drinker in the home, so I only have two kegs on tap. I have a 3rd keg that's my fermentor that I try to keep full of fermenting brew. When one of my serving kegs blows, I sanitize it, and close transfer into it from my fermentor. Since my keg-emptying rate varies, sometimes my closed-pressurized fermenting brew will sit for a few weeks, but it's usually closer to the 10 day schedule outlined above.
My brews have been fully attenuated with this method. I am allowing the fermentor to get a little warmer than I usually do (ambient high 60's instead of low 60's) to allow it to ferment quicker. The pressure supposedly suppresses warm ferment off-flavors.
While I usually do this on low-to-mid gravity brews, I experimented on a 1.080 OG RyePA. It took about 4 days of cold crashing to fully clarify, so more like 14 days until I was drinking clear beer (although I was gladly drinking cloudy beer at 10 days). It fully attenuated in that time, so unless I got lucky it seems like you can pull off a quick turn around on higher gravity brews too.