My short answer is experiment and don't be too concerned about 90 versus 120 XY stereo. These are approximations I'm convinced were chosen mostly to generalize about image based upon some suppositions about how a recording might be made, which would differ completely in most of your applications.
I'm more accustomed to field audio for documentary audio, rather than recording live music, but I'm interested in this topic and otherwise enjoy this site. Historically, there have been lots of theories on stereo mic placement. A look at classical music recording philosophies, including French Radio's ORTF, Holland's NOS, so-called X-Y and Blumlein have gotten attention among sound enthusiasts, but whenever I read interviews with old sound engineers from stereo's early recording days, it's clear those are just a few. Heck, we've never really settled on how far apart speakers should be, or rather some stereo listening guides may have, but given the amount of listening done in automobiles and, particularly headphones, there's obviously no true one-size-fits-all recording methodology. I'm still astounded that after all these years the vast majority of public radio documentaries are done in plain vanilla monaural! BBC seems to have discovered stereo, but recording notes are almost nonexistent. I know a retired BBC engineer, who claims he did a lot of Mid-Side recording, but the shows I hear are all over the place.
I collect stereo microphones. One company who departs from XY slightly is Audio Technica. I own a couple of their mics that feature 120 degrees. The hole in the middle isn't a problem. Some image wavering is and can sound weird if you're, say, recording an interview and the subject wavers back and forth. Otherwise, no problem, and the backdrop is wider, which can be appealing. Sony has issued a number of Mid-Side mics, which allow you to electronically dial-in a soundstage. I find something between 90 and 120 is ideal for most of my purposes. At 120 still no problem. There is some mono incompatibility above 120. My favorite monitor phones are AKG DJ phone with a stereo-mono switch so I can judge summing compatibility in the field.