hello, welcome!
Yes, a moss layer helps keep moisture in, but it gets mode difficult to water the plant.
Aesthetically the moss is very nice anyway.
As for exposed roots (Neagari Stile) it is not so good with this "S" shaped trunk, so I would skip it with this tree.
Congratulations for keeping it alive! But as said, if you have a place for it outdoors it will be happier.