Three I think. Maybe four.
Out of curiousity how are the asexual characters used? Are they portrayed as plot heavy side characters that push the story forward? Can you as the MC move them from their position of sexuality?
I can see asexual character only working in very specific cases in porn games, personally I think they are a terrible idea as a 1 scene character that has no sense of progression especially in CoC 2's format as a game. I really wish I could remember how the dungeon works though and how to get the horn.
I play 4 characters as for race it differs for me.
-Straight dominant male starts as human barely transforms mostly to get massive balls and a huge equine dick. In this playthrough I try to play it as straight as possible which is surprisngly hard considering how many things like to ream your asshole.
-Straight Switch female starts as a Lupine but have had cow and plant-like transformations in addition. Mostly start as Lupine for Garret content. Also have done bimbo females so I go full submissive in those as well and keep Brint as Brint.
-Bisexual switch Herm starts as elf but will just transform to anything as I mostly use this character to experiment. Have done corruption variations where I go succubus futa with a dominant personality too.
-Bisexual submissive male will get transformations that keep them really feminine but lose their male equipment. Also keep Brint as Brint here.
While I do enjoy the TF aspect especially if it plays into the character the scenario for me I don't have as much enjoyment if your TF feature is barely commented on in a sex scene or sometimes ignored completely. For me if I am playing a submissive character forced transformations on the player with characters are fun for me especially if it plays into the character's story. Even mental changes are exciting for me and TiTs does this well with I think its Lain who hypnotises you and the cum addiction from Ardia so you become their sub also the option of becoming their alpha makes her super submissive which is fun too. As for my dominant characters/ corrupt characters I like the fun of transforming others like Kelt and Arian in CoC or if I want to be a complete asshole to corrupt pure characters like Jojo and Marble.
As much as I love Brienne I am not as big a fan of how it takes place for example I would have preffered if Brint and the PC were experimenting with something and it was a progressive accident where you can decide together with Brint if they like the changes and want to keep progressing down this route. Rather than puttting on armor that changes Brint into Brienne overnight with the game warning you that you are a cruel person if you don't send Brint to Sanders right away who is a few meters away from where you are staying. Similar with Berwyn/Wynne if the writers put in maximum effort I would have preffered that since they became a lesser god-like entity to have a malleable form that can change regularly also if they were dominant with you in the past to remain dominant so even without a penis they would dom the PC. Also to expand on the pregnancy content like interacting with your child instead of removing the content as if you never had children with Berwyn/Wynne.