I recall one game on the sidelines they attached something to the crown of the helmet and it looked like they were pumping it. Are some helmets like the Nike pumps where you can form fit the head with air pockets?
Yeah. Each helmet is inflated to fit the players head nice and snug.
And I'm sure helmet and facemask type are up to the player. Though with visors it's a bit different. I'm pretty sure you have to have a medical reason to wear the dark visor like LaDanian Tomlinson wears.