[?] Flashing TWRP AFTER + magisk + rooted?

I have a HD1907 as well. Although I kept mine tmobile for simplicity, since I end up flashing lineage 18.1 over top of it, then nethunter linux so bloatware isn’t an issue.

My understanding is that there isn’t really a need to flash twrp over your recovery. Most of its usable functions can be done with fastboot boot twrp.img. However, if it’s something you just want to do, it can be done. Magisk patches your boot.img for root, not your recovery, so I don’t think it triggers any wipes or reformatting.

Beyond that, if you wanted to revert it, you can use a payload dumper get an unmodified version of the recovery.img file from the last OTA you used and just reflash that over twrp.

Last thing is, these are A/B partition devices. Mixing up flashing/installs between the two partitions is easy to do and can lead to bootloops and softbricking, requiring a startover from MSM tool. Might be more that I’ve missed, but that’s been my experience with that model.