i sometimes use them with a ‘enduro helmet’ when its sloppy.
They only restrict breathing if you buy ones that dont fit your face. (my oakley o frames are great my 100% i`ve had to trim the foam by the nose)
vision wise ive not noticed much restriction – some goggles are better than others. Melon optics are supposed to be really good.
They do steam up when not moving – again you may need to remove some foam on the vents
they also get covered in crap and you cant see (much like yr eyeballs!)
dont wipe the grit off run some water over the lense.
strap outside of helmet.
you might want to consder where you stash them for climbing as some helmets the peak prevents you just shoving them up a bit. (i tend to run mine sideways it looks stupid but it works)