I used a gopro helmet mount strap (one that goes through the airvents) and didn’t like the camera weight on top of my helmet, and like you said, I was always afraid I would adjust it badly (had one video of the nice sky above, another of just the road). Not so shabby example here: Orahovica Descent - YouTube
Best mount IMO is on the handlebar, I have a k-edge garmin mount with a gopro attachment under the garmin, so it sits just below the handlebars. You can see an example of how it looks here: BK Zadar Mali Krug - YouTube
If you want more of a first-person view, I would go with the chest mount. You can also use the extender arm to put it closer to your head. These videos look more dynamic, since they include the handlebars, front wheel, and they kinda move where you move. Kutjevo Climb - YouTube