I wrote about selectable or non selectable romanceable characters on my IF advice blog here if you’re interested. There’s also a lot of discussion in past threads on this subject including here.
Ultimately there are positives for both ways of doing it for romanceable characters, so you should do whatever feels great for you.
For the PC, it’s worth being aware that for the most part genderlocked MCs are less popular overall. But again, go for the setup that feels best for you and the story. These projects tend to take a long time so writing something you’re passionate and excited about is important for motivation.