Quick update, after actually watching my P3 as best I can with respect for safely driving:
I'm stock tune. AFRs tend to run a tad rich right after PSSSHT noises, so I believe it's accurate to say the car is trying to accommodate for that continued spool where it's venting to atmosphere instead. However, it's not overly rich -- upper 12.x-low 13.x AFRs, then right back to a pretty steady ~14.3-14.7 range. So I think there may be some accuracy to the statement that you give up some power/speed/spool time for the sound, not sure if it causes any issues on stock trims but I figure if it starts giving me headaches, I'll revert back to DV-only. But for now, for a car that I really just enjoy on the weekends, it's entertaining and I'm fine with it. I figure a little rich is better than lean, and I'm having fun.
I don't think I'd replace the whole DV assembly with a BOV though, as it is around town it's quiet and well-behaved, but easy enough to coax moderate sounds out of it when I want. Nice middle ground, and easily reversible. I've been hearing that every so often the rubber seals on the spacer need to be checked/lubricated with oil, so I'll likely do that in the interest of testing and see how it holds up.