Thanks. I think the video embedded in the earlier post here
does a pretty good job of letting me know what I'm giving up in terms of tone mapping in native DV vs. artificially converted HDR10. Granted, the reviewer in that video is using a 2017 LG B7 OLED and I have a 2016 LG B6 OLED, but close enough.
I think my game plan, for now anyway, will be to leave the ATV4K set to 4K 60 HDR10, with Dynamic Range Match turned on and Frame Rate Match turned off. I'm very pleased with how the ATV4K displays motion/judder at 60Hz across a range of content I've looked at. And while I was getting a weird flickering effect in near-blacks before with upscaled 4K at 24 Hz, I've yet to see that on my TV if I keep the ATV4K output at 60Hz. So that's another bonus. And the ATV4K does a better job of 4K upscaling than my TV or Yamaha receiver.
I've verified that the main apps I use -- Netflix, Hulu, Showtime, HBO, Channels, PBS -- all work with Dynamic Range Match so that everything switches to SDR for native SDR content (which is most or all of those apps' content).
When I watch the occasional DV movie in iTunes, I'll turn on Frame Rate Match, allowing the ATV4K to pass a 4K DV 24Hz signal to the TV. Otherwise, I'll keep Frame Rate Match turned off. Maybe a third of Netflix's 4K content is in DV. I'll probably just let the ATV4K convert that to HDR10 at 60Hz (i.e. Frame Rate Match off). From what I've seen so far in bits of Mindhunter and Lost in Space, it looked fine.