Hello, literally anything strings could go on that, I currently have BG66UM and does me good, so it's really what you prefer.
I tried 66UM with my NR900, it didn't work for me. However I have switched over to NBG98 and I like the feel with it. It is individual preference after all.
I used bg66um and I liked it. But the string broke after less than 8 hours of playing. Been using the racket on zmax65 now and has been good more than a month. Personal preference. You should try various strings if you are very concerned.