I'm sure you're going to be able to grow HC with your set up.
My 2.5gal has a 13w fixture directly on top of it; 8 inches from the substrate. I've grown fissidens moss, java fern philippine and windelov, anubias, and the easier crypts. I don't have DIY co2, but as far as I can tell, my plants are doing great.
Don't forget that you also need to use fertilizers. Since you're not planning to use a filter, atleast a small power head or airstone so there will be circulation in the tank.
Currently out of the hobby
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