I know that there is 2 main choices, that can't be undone - cici quest end and who to move in with, so 1 is there more of thouse questions, and 2 what wariants is "cannon"/"best"/add most amount of content?
Choosing to help Cici locks you out of any further experiments with Kali, any experiments with your character, and locks you out of the Tiffany sandwich ending, but gets you a different gain sequence with Tiffany. Choosing to help Tiffany locks you out of the Cici sandwich ending, you also kind of feel like a monster, but considering all the other stuff you had been doing, it's about par for the course at this point.
While Beth and Jamie definitely have their benefits, if you are looking for the most amount of content, you should choose Stephanie as moving in with her gets you an entire D&D campaign with two other girls gaining weight.
All options are 'Canon', there is no 'best' option, but for the most amount of 'content' choose to help Tiffany and choose to move in with Stephanie.