I'm a DO that recently matched and I would suggest taking both exams. While it is true that more and more programs across specialties are becoming more and more adept at interpreting COMLEX scores, they are ultimately still more familiar with the USMLE. People do match with only COMLEX, but I had numerous times on the interview trail when I was thanked for also taking the USMLE. It makes their job "easier." Naturally following this was the question, "But why did you take both?" It's a benign question and I was honest. I wanted to keep more doors open. If I had changed my mind at the last second to another specialty where most programs only wanted the USMLE, I'd be prepared. In that respect, I think PM&R is ahead of the game in accepting COMLEX: I believe almost all programs will accept just that score alone. I believe this same question was answered by some of the attendings on here in a post not too long ago.
IMO, if your COMLEX scores are average to below average, definitely try to do well on the USMLE to optimize your chances. USMLE step 2 isn't necessary unless you are a masochist.
As far as score ranges: I've never liked the idea of a range. There is no top limit. Rather, think in terms of minimums, and concerning that I don't have an answer. Maybe others involved in the process can chime in. I've heard whisperings that people with <210 have matched. PM me and I'll let you know what my scores were and where I was offered interviews.
Also, keep in mind that boards aren't everything, although they feel like they are. I was always told that PM&R places more emphasis on you as a person than you as a score. I never believed it until I began interviewing and academics rarely came up.
In short, take both. I don't know if you've taken it already, but the COMLEX is a crap test. In fact, I actually enjoyed taking the USMLE after that nonsense (maybe I'm the one that's a masochist?).