If I choose to go with three microphones (two adjacent NOS setup with slightly reduced angle and increased spacing, sharing a center) how important is microphone matching? As I don't have three identical mics the closest I could get would probably be the 461s for L/R with a 414 center (I'm assuming I would use the cardioid polar pattern for the 414).
Not critical. Decent matching is arguably a more important when recording in a more uniform soundfield. On-stage and relatively close to the instruments you are sort of in a zone that lies between mic'ing the full ensemble with a single stereo array (where matching is somewhat more important) and individually spot mic'ing the three instruments (where it isn't). Sort of a blend of both approaches, which is one reason I think it works well.
That said, always nice to use the same mics across the primary stereo array, as the identical response helps with consistency of image, smoothness across the soundstage, and the sense of depth. I'll usually put the different mic in the center to maintain L/R symmetry, so any difference in timbre, which may be most apparent in the ambient/reverberant part of the recording, will manifest symmetrically across the center verses the sides, rather than one side verses the other. Consistency of response/timbre is the general goal. Polar pattern not so much. You can use a completely different polar pattern in the center without a problem. In your situation where the L/R angle can be somewhat wide without problems it might help to use a somewhat wider polar pattern in the center than the sides, but should work fine using three cardioids.
In my OMT arrays I go back and forth between using identical mics across the L/C/R triplet to using a different pattern in the center. I usually like using three identical mics, but have recently been switching to a more directional shotgun mic in the center when I want to nail a clear and distinct center from somewhat more of a distance. Which is in a way, sort of the opposite of your on-stage situation. Horses for courses.
Years ago, I did a lot of on-stage acoustic jazz trio recordings over the course of a couple years, and settled on using three AKD TL's set to supercardioid pattern, placed as low as possible to the stage floor, arranged in a triangle with about a 90degree angle between the L/R pairs, angled up at the players positioned to either side of a central drum kit, with the center mic pointed up at the snare, just off center of the kick to avoid the direct "whump". The supercardioid pattern helped with the narrow 90deg overall angle between L and R mics, and provided a bit more separation from the audience, which was being picked up by another dedicated pair facing out into the room. The room/audience facing pair was very nice to have but not strictly necessary, but that three mic arrangement worked so well it became my go to for on-stage recording, and was later worked it into most of my recording arrays. I like the three mic' stereo thing for taping.
