Isekai is a great concept that I have daydreamed about since I first played RPGs as a child, it's honestly just a fantasy subgenre but JP likes to explore those a lot and play off of those tropes a lot.

A lot of isekai is garbage, but I am not sure what you would mean by proto-transsexual in this context to be honest.

For reference my favorite fantasy/isekai have no trannies in them, or sex changes for characters, but I will read new series to see what they are like and it is how I find things like that.