OK - Exfog is a doddle to set up. The XT's come with the little magnet hose things, push the adapter through a hole in the seal vents (desert locust for me), point at the lens and you're golden - don't need to make any destructive holes or anything.
If you have active headsets, you are going to hear every little bit of it functioning, but its easy enough to switch off when you don't need it.
The vent is on the bottom of the unit and the hose adapter actually creates an intake space, so unless you're using a really restricting pouch it will have plenty of space.
I got the XT without the headband for ~£50 from Specs4sports, which I think makes it about £10 cheaper than the Novshit. I could feel the air even on the lowest setting, and the full power burst mode is mental.