Specs say sanitize cycle goes to 170F

I'd call Bosch, since the manual is lacking that information.

according to bosch customer support,

extra 170º F 76º C

hot 120º F 48º C

warm 90º F 32º C

cold 60º F 15º C

what's the appropriate one to choose for garments marked for 40º C?

40c is considered warm in Miele info. So since it is 104f, It probably do the 90f in the Bosch. In Miele, 120f is called very warm. 140f is hot. I have washed things in 120f without issue in my Miele, that probably call for cooler temp. Some things, I definitely stick with cool water and on handwash or wool function.