2 ch vs 4 ch. Two channel delivers a stereo image, having a left, middle, right spread. 4 channel provides a pair of tracks that can be manipulated into a surround image (left, right, middle, back left, back right) or flattened into a stereo image.
So look at how you set up your instruments and/or amps - are they in a line or in the round?
The Mid-side vs XY is really mainly a sales gimmick, since the two are mathematically and sonically equivalent. The real question is, front or back mics. If you use the XY front pair, you can see the meters from the performer position. If you use the MS back set, the audience (or engineer) sees the meters. Do you have a recorder operator or is it operated by the band?
Don't let these options stymie you. Turn the darned thing on and try different configurations. Record yourself even if it's just slapping rhythms on your knees and singing nursery rhymes. All you're really trying to do is learn what the buttons do, get a little bit of synapse path building going on.
Then when you fire up to record the band, pick one setup and use it for two songs. Pick another, use it for a few. Work through the options. Listen back at your leisure and decide which technique works best for you. The cost is $0.00, the benefits are huge, so take advantage of that most excellent of teachers - experience.