I was given a couple of gopros. With handle bar mount they work fine and with all the other clutter on my bars, nobody ever notices the camera so not likely to cause concerns. FWIW I don't like people taking pictures or videos that clearly show my face (or other obvious identifiable features) without asking first, but I'm old, etiquette has changed and in public places as has been pointed out, is legal. I usually just block my face with my middle finger extended when it's obvious someone is photographing me.
I've got other mounts which include chest mounts and helmet mounts. The helmet mounts have bottoms that are curved similarly to helmets and use VHB tape to adhere. That's considered permanent (they use that stuff for airplane windows, etc.) although it could be removed later (unlike epoxy). Velcro won't work since the camera will wobble around way too much and videos are garbage.
Personally I wouldn't consider doing a helmet mount though... looks too dorky/egocentric/attention craving (daddy look at me!) and it's very obvious you are recording, or at least might be. The handlebar mount much better suits my purposes. Very easy to turn on and off - you'll need a wireless controller for the helmet mount to work well. If I stop I can point with 180+° motion or even pop it out of the mount (takes literally a couple of seconds). Very convenient.
I've gotten some fun videos but frankly most of the time they're boring and it's more a novelty for me. I've got a video of a drunk neighbor driving his jeep into a canal, the cops chasing them down and later fishing the jeep out LOL. Then again the cameras didn't cost me anything, just the mounts...