If your goal is least maintenance as possible than rather steer away from anything carpeting stem plant. Almost all of them require ample co² anyway to grow fast and dence.
And growing fast and dense requires regular trimming to keep the lowest part at the substrate healthy. Gras like plants in high energy all tend to grow quite tall +5cm, again regular trimming to keep it low and make it spread.
In low energy i personaly would suggest grass like plants, they will grow less tall but also relatively slow.. Currently growing Lileaopsis brasiliences, dwarf hair gras, dwarf sage and crypt parva in low energy. Depending on the number of plants you start with you need a lot of patience and time to make it spread. Dwarf sage grows the tallest of the 4 and runs (spreads) the slowest. Crypt parva is so slow in my experience barely see it grow in years time. Dwarf hair gras stays very small and runs agonizingly slow, but it can handle very low light and stays healthy. A valid candidate but you need to plant a lot to make a carpet or you need to wait years to carpet and spread on it's own.
My curent personals best at the moment is L. brasiliensis.
Started 2 years ago with a few plants only.. So picture bellow is 2 years time growing. In this low energy setup with a rather well fertilized soft substrate i experience it rather spreads than grow tall. Never trimmed/replanted it all this time just let it grow its own way.. I guess it needs another year to fill in the gaps on its own that are still there to see. Helping it with replanting should definitively speed up the process, but i just don't it's not my goal, i like to see what it does on it's own.
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Also grew this plant in high energy setup, than it more likes to grow tall +10 cm and requires trimming to keep it low and trigger it to run and spread. In this low energy setup i didn't do zip only planted it..
I've had the same experience with Helantium tenellum many years back of which i do not have pictures.. Also do not know the true var. i grew that time. According description i suspect it was the North american HT var. parvullum that should grow less tall than its south american cousin which is currently more common in the trade.
About mosses, i woud say yes if you take a Taxiphyllum sp. But a fissidens is not realy a spreader on its own, this would requirer a ton of it to plant it. ANd fissidens is a little dirtbag as well, definitively high maintenance if yu manage to create a carpet with it..