Consoles have aim assist for FPS shooters that computers do not. You will find your aim using a controller on a PC game to be very bad.
As silly as the term "pro" sounds I'm a former pro halo PC player. Not a single person used a controller in our league for that reason. I currently play CS GO and don't know anyone who uses a controller. You can try if you like but I think the results will be pretty bad compared to a mouse and keyboard. Especially for CS GO the hitboxes are tiny, you might be able to get away with it playing as a Demoman in TF2.
I do have an emulated version of smash brothers melee that you can play online against people, a controller is very handy for that. I'm trying to play with a keyboard and it is impossible due to the sensitivity and keyplacement.
When you aren't using a mousepad all you really need to worry about is whether or not your desk is smooth and non-reflective. I didn't use a pad in my pro days and had no trouble with it. In fact when I had a steelpad it would sort of heat up from my hand and develop a reflective spot.
Edit: I'm not sure if reflective is the right term, but you'll know it when you have it. It might actually be the opposite of things being absorbed or refracted. It happens when I play on something white or when my mousepad would get condensation on it. Your mouse kind of wigs out and loses responsiveness.
Let me know if you want any tips at CS. I'm fairly good at it.
