You might have to change some settings in Arturia’s MIDI Control Center application to ensure the knob range is working OK for you with Rack.
For example the attached screen shot shows a change I made to Knob 1 on my MiniLab MKII. Note that the Option setting is set to “Absolute” and Minimum and Maximum are set to, er, the minimum (0) and maximum (127) values.
I’ve found that if I don’t change those settings in the MIDI Control Center application (and then upload the changes to the MKII) then I can only “wiggle” the Rack knobs very slightly if I use the default settings on the MKII.
It might work differently for you, but letting you know just in case. 
Update: Also, the keyboard works fine, and the pitch bend and modulation “sliders” work fine (don’t forget that you have to use a module like MIDI CV / MIDI CC to use them as modulation sources).
To use the pads I’ve found that setting their mode to Switched Control in the MIDI Control Center application, Option to “Gate” and then using a “spare” / undefined MIDI CC number (e.g. 20 to 27 for pads 1 to 8), and then using the VCV MIDI MAP module to map the pads to a module’s button (or gate input / trigger input if they have an associated button on the module) works great. (See the second screen shot).
