As Bob alludes to: Do you have experience friction shifting 10 speed cassettes? 9 speed ? less??

All people are different, my experience is that I am fine with friction up to 8 speed but not beyond. On my two commuters I run 8 speed friction, and have 5 speed friction on my Cycle Pro Ram. On other bikes I have 7, 8 and 9 speed indexed.

My touring build (in progress) has a 50-39-30 Shimano crankset, 12-36 9 speed cassette, Shimano M592 RD, Shimano road triple FD, Microshift 3x9 brifters. 30-36 may not be low enough.