Can only comment on this latest (Monterey) being the same as Big Sur public on this new M1 and it is slow and clunky when the library is on an external hard drive. Slow to do anything which is a shame cos if you plonk a cr2 file on the desk top and let affinity get to work affinity is quick. Try to do it through external editing function in Photos and time to go put the kettle on and wait. Reality is the library is too big for the internal drive.
Stable as in no crashes. Probably too slow to crash.
Face recognition, it just seems to get there, a few missing but not a lot. I have not noticed any real issues there.