Gamespeed: would increase the amount of plays per game.
I really don't see affecting gameplay, other than the human side having to adjust and react faster. It could actually be more difficult for the user side. I haven't tested it, so let us know if you do please.
Increase hum tak to 50: This will cause a few things and only make it easier on the Hum side.
1. It increases the range in which you can tackle, making it easier to shutdown the cpu run game and easier to get big hits/force fumbles.
2. It makes block shedding easier for the user, so it's easier to stop the pass and run.
3. You won't see as many moves by the cpu ballcarrier b/c the improved tackling nullifies any special moves.
I've tested the tackle slider thoroughly and it's probably one of the most sensitive sliders. Move it any lower and expect the cpu to break alot of tackles and move it to 50 and they rarely break or avoid tackles. So if anything move it 1 click up at time from 45, until you get your sweet spot.