I have never seen an argument against running the latest version, 9.2.2, on anything that can. Maybe there is some software that prefers earlier versions, but as someone who never really “moved on” from OS 9, my old Macs have been on either 9.2.2 or 7.6 for many, many years now.
All laptops that say MacBook are Intel, they won’t run Mac OS 9 at all. Those are from 2006 at the earliest. The last few years of PowerPC Macs won’t officially either, including as I recall all the aluminium G4s, all G5s, all Mac Minis and some Powermac and iMac G4s, as the link doomglue posted explains. But if you go to macos9lives.com, there’s a modified image that runs on just about any G4. I’ve not tried it, though.
All PowerPC Macs running OS X before 10.4 support what’s called “Classic environment”. This isn’t emulation but it’s still not exactly like running real OS9 (it’s closer to a virtual machine), and one of the things it’s not good at it is things like MIDI and real-time audio, but I think some things do work. It runs the Mac OS 9 apps in windows alongside OS X windows, with things like copy-paste integration.