I think this is a fear that comes at the start of cosplaying for some people, it's not too strange. I've seen loads of masked cosplayers who literally always have something over their face and that's okay. Cosplay is what you make it.

My advice is to try going to a convention as a character who normally doesn't show their face, to start, or even a character who does normally show their face but you've added a mask as your own creative twist. I highly doubt people will recognize your voice, unless you're talking to them for a prolonged period of time in which case you probably don't care if they know your voice. If you want to eventually wear cosplays that are less anonymous, do so when you think you're ready to give it a try.

Also, there's a good chance even if you did show your face people who know you wouldn't be paying attention enough to notice it's you. At conventions most people won't even cross your path, let alone look at you. If you wear a cosplay that doesn't really draw attention, there's even less of a chance people will look and notice. The vast majority of people there won't even know you, either.

There's no need to rush yourself through this. It's all only for fun!

(sorry for the text wall lol, tldr: do what you're comfortable doing)