You will want to assign your sims the orientation you want them to have as well as selecting "no" on if that sim is romantically exploring.
The only behavior change was the way in which social bunny and gameplay will effect the orientation if yes or no is checked in romantically exploring. If it's set to yes the sim will become romantic with both genders. If set to no they will only accept romantic interactions from the sexual orientation you pick. Social bunny has a way of creating romance meters on its own especially if the exploring romantically is left checked to yes.
No they don't autonomously woohoo with sims they don't have a strong committed relationship with and woohoo can't happen until a first kiss is had. Some of my married sims will autonomously woohoo but it's been that way before and after the update.
