I don't find "masking" to be a helpful term, although I use it myself.
I don't think that there's a genuine me and a mask. I change depending who I'm with, and some ways of being are more painful, some feel more right. There might be multiple ways of feeling right.
This might be because I'm late realised, so I've spent decades forcing myself to behave against my nature, so some of that has become my genuine nature, like a tree forced to incorporate the wires wound around it in its shape.
Some things I have identified as harmful masking:
Being self deprecating about my special interest.
Conciously making myself less intense
Pretending to agree with people when I actually don't
Making my face and voice expressive so I don't seem angry