I’m comfortable being a woman with my lady parts. I also like to pretend. I told people I was male (transmasc, specifically) so that I could freely experience attraction to just men without having the “straight” label.
Whatever I was, I did NOT want to be straight, so presenting as a trans guy helped me feel better about myself. I could be a gay man. Then, I was a non-binary demiboy (either gay or bi but would only date men).
I felt like a girl in real life. I still do. I didn’t feel dysphoria nor a desire to transition in any way, neither socially nor physically nor anything. It just felt relieving to be a gay trans guy, but that still made me trans even though I didn’t identify as male nor did I ever see myself as male, right?
(I see myself as a woman and always have, I don’t have dysphoria. I identify as a woman who wants a penis. I think I’m moreso attracted to the idea of having male parts than actually seeing myself as a guy, but like I said, it relieved me to be gay and not straight.)
long story short, I’m a woman slightly attracted to the idea of herself being a trans guy or having a penis.
First of all, gender expression and being trans is a vast field. While there are a bunch of labels one can use and that fit for many, this doesn’t cover everybody and their experiences.
Second, there are many forms of dysphoria, not all have to do with being uncomfortable in your body.
With understanding this and only having your description from this post, there are signs of both of this (at least some I interpreted that way while reading). As far as my understanding of the demi label goes, one only feels like that gender in certain situations or at certain times. If that is “on the internet” for you, then it isn’t far fetched. While you feel comfortable as a woman, you also said you’d desire male genitalia, which even without any pain from it is still dysphoria. If you want to be perceived as male sometimes or just online, that’s a form of dysphoria too.
I’d recommend to you to do some soul-searching and introspection to find an answer for yourself. It doesn’t sound like you’re trans-masc, but maybe demiboy, genderfluid or non-binary would fit you? Nobody can answer that for you though and it is fine for you to be something that doesn’t have a label.
Now I would say it’s kind of inappropriate to call yourself trans-masc online if you don’t consider yourself that. It might be seen as appropriating an identity or pain you don’t actually have. Many trans people suffer from their dysphoria and taking that label just for the optics is maybe not that nice (similar to how people pretending to be another race isn’t a good thing). Connecting this to my previous point: many trans people do start out pretending to be another gender online to experiment. If it feels comfortable to you, maybe you should think about that a bit