I wish there was a clear cut outline to lay out exactly what every seminar is like…but i want you to know that same type of girls can apply to BJJ Bnos Chava, BYA and BNos Sara and then when acceptance letters arrive, girls decide where they want to go…so the group dynamics which you are asking about will change every singel year in every seminary…thats why you hear that some years this seminary had a fantastic year while another seminary, girls didn’t like it that much…
but you can never really know what type it will be that year until you go there…
however u were asking about BJJ and Bnos Sara…I heard Bnos Sara is warmer…thats from my friend’s experience.
and just like with everything in life…it pays to daven to Hashem that He directs you to right seminary cuz this is one of things in life where you need mazel as well!!
good luck!