MV-HEVC files play normally in unsupported apps, so it should look fine. The test would be to make an edit removing something and export it as MV-HEVC and see if it is retaining both images. If it is possible to upload the export back to my folder I could check it on the Vision Pro.
It may be the case that we would still have trouble start with SBS conversions and then Resolve just takes care of the reinjection.
In terms of capabilities you are right - DaVinci Resolve 19.1 can encode and decode spatial video, and decode spatial photos.
DaVinci Resolve 19.0 could already decode MV-HEVC clips. The new features in 19.1 are the ability to decode spatial photos, and the ability to encode MV-HEVC clips.