I believe the control knobs on the GSR200 are a volume knob for each pickup and a tone knob.
Action height is really down to personal preference, there is no right or wrong.
As a beginner, the biggest mistake I made was not putting enough effort in to getting solid timing. Lots of scales played to a metronome, try playing patterns within the scales where you're not just going across the strings one at a time.
If you only play reggae you'll never want to use a pick, it'll sound wrong but if you want to play other stuff as well, it's a skill worth learning. If McCartney and John Paul Jones weren't to good to use a pick, none of us are.