Too much moisture can cause root rot. Let it dry out entirely before watering again. That's likely why the leaves are curling. I usually use 1 part potting soil to 2 parts perlite/bark (so one part each). Bark holds moisture as well, and you want that soil to be chunky. In the words of a plant YouTuber "drown that ho" when it's time to water but let all the extra water out (if indoors you can water in the sink/bathtub/sterilite tote) because that extra water will allow for all the nasties to populate and eat those roots away with rot. And you'll be none the wiser until it just drops over dead one day.

The trick with growing them in water is you have to change the water out pretty regularly or the same thing will happen and you have to provide the nutrients that they are not getting from the soil when it's in water. Fish tanks are amazing to grow pothos and monstera in because they get all that lovely fish waste directly into their roots, and the water is being filtered by a hob or sponge filter etc.

When moving from water to soil, it's going to be a shock, and growing in moss does help that. You can also grow in moss+perlite+bark+soil, if you live in a hotter area (or your house is hotter) and heat sucks out the water from the soil faster. The moss will help keep the soil moist without being sopping wet.

Does any of that help and if not, hit me with your questions and I'll geek out all over again :)

Edit: also when moving from water to soil, let the roots "harden" by drying a bit! That way they have a "crust" on the outside kind of, for lack of a better way to explain it!