Hi & Nice work you're trying to do w/ the patients, I respect the effort that likely takes.

Fussy & anxious aren't great for plants (especially if also done w/ frequent watering). Also fussy/anxious isn't helpful to patients w/ mental illness who often have more of that than helpful to begin with).

That 1-1-1 (commonly called soilless mix) mix isn't that awful for Houseplants, they'll be OK (likely fine). But not for succulents like Snake plants. Both peat & vermiculite hold water so that will likely keep the mix too wet.

For succulents, just use any mix you can find (AV mix or Cactus & Succulent mix, even if MG's) w/ extra 50% perlite & that will make it fast draining enough.

Often w/ plant care, the less the better.

I've kept a lot of my plants going for years perfectly well in standard potting mixes - snake plants, ficuses, the list is long. but I am an under-waterer and I do not repot often - the root mass is dense, so peat and moisture is not a problem at all.
and I am not planning to repot any in gritty or 511 either.
so relax, and if in doubt, cut some with perlite/orchid bark mix. and do not water to dripping every time. let them dry up , check with a chopstick/skewer : like a cake test, if it's moist - do not water. and you'll be fine.