"Does R3 feel harsh compared to the RS?"
That is the first time the word harsh was ever used in the same sentence as a R3. They designed these bikes to ride the cobbles of Paris Roubaix. These bikes are as smooth as a baby's behind. The RS is just designed to ride a little more upright.
I am 52 years old and have a bad back and I can ride my R3 all day comfortably. You can't go wrong with either bike as long as you get the right size and are fitted on it properly.