I would correct this slightly - with CoG you can play as a variety of genders (with non-binary MCs always available in games published after 2018-ish) but ROs aren’t always romanceable without limitations.
That said, as others have said there is an expectation for ChoiceScript games that there will be some degree of customisation.
I do find that a there’s a lot of variety in what players consider a “set main character” or customisable. If a character’s backstory is set, but their name and personality can be shifted, where are they on the set/customisable spectrum? How much does appearance-setting affect immersion? It varies a lot from person to person.
I notice in threads like Options you want to have more often that there is some desire for MCs with more defined traits. But anecdotally, I also see requests for very detailed appearance or clothing customisation, or requests for MC responses that don’t always make sense for the setting or drive the plot forward - which is something to bear in mind when deciding how defined or not you want your MC to be.
Some very popular games have more strongly author-defined MCs. Others are a lot more “blank-slate”. I’m going to throw in a big bundle of links to threads on the subject for further reading - it’s definitely not a topic on which there is a cut-and-dried answer. On this post there are even more links for your perusal!
