With regard to movement speed, it depends on how you are commanding the motion. If you are using the jog buttons in Mach (press TAB to bring up the jog screen) then the speed will be whatever percentage of your maximum is displayed on the jog screen. The maximum (rapid, G0) speed is what you select in motor tuning. You should set this up first to be the fastest your machine can move, at all positions in the working volume, without stalling or losing any steps. Then take a bit off that for safety. You might find this is a little too fast for you to feel comfortable, so you can set it lower. As long as it doesn't lose steps when performing G0 moves, you are good. The acceleration is used in the same way - the highest you can have without missing steps.
If you are running G-code, through either an imported file or in the MDI screen, the feed speed is set in the code. But it still CAN NOT exceed the max velocity you've set up in motor tuning. For example if you have set 1500mm/min as the max x axis speed in motor tuning, and your code commands g1x100f2000, you will still only get f1500 movement speed.
Also, remember to check the feedrate override on the main Mach screen. This can be set to a percentage of the code-set speed.
Good luck with it, you will not be sorry you went for CNC. It's great!