Subwassertang is a single cell plant and once established you can make and do anything with, I also like to use jarva moss in all my tanks grows fast great cover for small fry and shrimp, tha main plant in the centre is subwassertang
I had some Java Moss that was doing well and suddenly it almost all died off. Now I only have a few small sprigs that develop shoots from time to time. All other plants have no issues. I think maybe my nitrates dropped too low and it lost out in competition with the Anubias and Java Fern.