Slider talk outside of the slider thread! Very brave
As far as I'm aware, turning the speed up will make every ball faster, but that kind of defeats the point for a medium pacer as you'll be bowling faster if you pull the min bar higher.
Visual speed is the one that is purely visual, but I don't know if you'll get more bounce per se. That isn't something I've tested.
You could increase the general pitch or ball bounce sliders, but you might want to keep an eye on what the quicker bowlers do as a result. You may make them unusable as they now can't get a normal delivery near the stumps.
If you're in career and only controlling one player, that might not be as much of an issue, but I suppose it would be when you're batting.