Thanks so much for such an informative response Will!
I'm excited to try more sphagnum propagation. I just set up a sphagnum propagation box last week, I've found two rotten leaves this morning (at type of pothos or philodendron I'm not sure, it's variegated), but they had very short petioles and the leaves were touching the moss so I'm not sure if that could be why. Anyway I'll try to keep learning more about this method as I think it could be a good fit for me when i get it right. Thanks again