Does an oil catch can have to be mounted next to the header?
 

Ive read that you need to mount an oil catch can next to the header so water can boil off from the heat. Is this something that you have to do or is mounting it near the intake manifold fine.

What? No.

You have read incorrectly.

The catch can catches this nasty water/hydrocarbon crap and you have to manually put it in your waste oil container.
If it's catching good quality oil it's not working properly.
Mounting this crap anywhere close to high heat is a good way to burn up your car.

I'll bring the marshmallows...

Running the engine oil temp above 212 degrees IS a good call. It will turn any water in the oil into vapor which is then caught by the catch can.