1. Yes, just ignore the knob and use the fan controller (set the knob to max and leave it at that), but why not leave it at the control of the bios / whatever software you have?
2. I wouldn't recommend that fan controller, do you only require 4 channels? Are you intent on a touch screen? Lamptron FC5 is a very good 30W/channel 4 channel controller but not touch. If you want a touch screen either the NZXT Sentry LXE or the Lamptron FCT are the better of a limited selection.