1: I've often tried to bribe somebody some time ago, due to my good experiences with that in M1TW. But I've never managed to succeed, so the rate of tries dropped slowly... Even if I try from time to time again, now with much more money in the bank :), but they always deny the offer...

2: I've never seen any negative consequences of missed nobles missions. I also understood the manual as there may be (1) rewards, or (2) penalties, or (3) both of them. So I never really wondered that missions without penalties exist (case 1).