8.1 as shipped on the orange iMac CDs has some support for USB, but it's pretty barebones, and 8.1 as shipped on a retail CD won't have those bits.
In my experience, anything that'll run 8.6 satisfactorily will almost certainly run 9.1 or 9.2 just fine, unless the system is so old that it's really better off with a nice install of system 7.6 anyway. (Like, if it has a 601, that may be the case.)
I do have a few PowerPC systems where I favor 8.1, such as with my UMAX C600, which has a 2GB~ish SCSI boot disk, and a 20-or-so-gig IDE data drive (formatted HFS+) and runs ASIP5.
In my experience, anything that'll run 8.6 satisfactorily will almost certainly run 9.1 or 9.2 just fine, unless the system is so old that it's really better off with a nice install of system 7.6 anyway. (Like, if it has a 601, that may be the case.)
I do have a few PowerPC systems where I favor 8.1, such as with my UMAX C600, which has a 2GB~ish SCSI boot disk, and a 20-or-so-gig IDE data drive (formatted HFS+) and runs ASIP5.