Do you play on any consoles? if so do you notice there is delay between you pushing on the joystick and the screen responding? If you don't notice this delay you won't notice the delay from a wireless mouse as long as it was intended for gaming.
A friend of a friend in his student dorm room took his router just next to his laptop, he told us that "This is to prevent any lag! My router and my laptop are just next to each other [it was like stuck together] I can get the best speed this way". And then we saw that he actually had a cat6 cable on top of his shelf still in the box.
even if yo get a crazy wireless mouse like the g700 which is around 100$ and 1000hz 5000 dpi whatnot and is supped to have 1ms input lag. there is like a TON of it. ALWAYS. because once your battery goes below 50% it's laggy as hell, once your mobile phone receives an SMS your mouse skips and in general it just doesn't feel right.