Experienced filmmaker here, Go for 60+FPS if your gopro will allow it. So you can do slo motion if you need to, I would leave everything else on auto so if you go dark to light it can change as if your putting a decent video of this type of thing your longest shot is only gonna be 5-10 max. I would also recommend spare batteries as GoPros eat them.
There are many places to mount, all with advantages and disadvantages
I feel that barrel mounted is the best start
With this you find your first footage is mostly of the ground, some of the sky, the rest is where the barrel is pointing and shooting - which is typically what you want to see
Once you've watched back how much the barrel is pointing down or up then you more consciously hold the gun up
An advantage with barrel mounted is that it works for the majority of cameras and doesn't add anything to the profile of the gun - there's a hopper behind the camera
With a head mount to the left or right side of your goggles, if you put it on your shooting side then you get a lot of footage of your hopper, if you put it in your non shooting side then you get a lot of footage of trees and bunkers.
On the top of your goggles is a good vantage point for footage, avoiding the ground or sky, but can also be jerky when looking around the area (even if firing a rope of paint on one spot you may find your head twitching left and right for awareness
With the exception of in front of your chin, any goggle mounted position for a GoPro or clone is a big bulky box making an easy target from the front. A tubular camera such as the contour or the generic 'barrel' cameras is more compact and suited to the side of your head
If stepping away from the latest branded camera, there are very good cameras at reasonable prices and you can quite quickly build a small collection such as:
1) barrel cam
2) head cam
3) rear facing gun cam - pointed at you
Then also perhaps a body cam, but front facing will tend to be obscured by your gun, though I have seen people with rear facing body cams on their back.
4) a sight cam - telescopic sights are only much good for some limited use in paintball, but having a camera stuck to the back of a sight gives a good zoom 'kill cam'
If you want to keep going for unusual angles then consider a camera on a pole strapped to your back
This has disadvantages in the woods but gives great footage