"What is the maximum number of conductors one may place inside EMT Conduit?"

singl or three phase?

1" emt @ (24")
#12 awg
20 amp ocp
# of thhn conductore are 26

1"emt @ (25")
#12 awg
20 amp ocp
# of thhn @ 75c conductore are 6+ground unbalanced

-single phase 9+gound balanced
-three phase 8+gound balanced