Gamer care about input lag. Pro gamer on PC don't use wireless input devices, they prefer cable based ones for exactly that reason. The input lag is also what (afaik) almost killed Gaikai. Sony recently bought it for some older PS3 titles. https://en.wikipedia.org/wiki/Gaikai
I never played at the pro level but I did play competitively and I would never use wireless internet, mice, or keyboards. These days there are some great mice, keyboards, and headphones but most people I know won't leave it up to chance and always go with wires.
Yes. I'm aware they do and manufacturers of those devices often provide options and information but cameras are seldom used as input devices so they're not usually measured and that's a shame.
