RE: Baggage overweight?

Working for res dep of one of the airlines you mentioned BatBay I can tell you that when you talk to a callcenter agent they will only inform you about the official rule, overweight charges are based on a percentage of the fullfare oneway eco ticket. As a pax, on a different airline, I was lucky enough ones to get awy with 32 iso 20kg but that flight was almost empty. I have the idea that it plays a role how full the flight is and how you present yourself at checkin.
“braun cells” is tricky, be prepared and it might help when you request permission upfront, call them and inform you want to take it.