For crypts, wendtii stays nice and small, easily fit in your 10 gallon. I have spiralis in my 10 gallon, but I went for the mad jungle look. They're draped across the top of the water in a tangle. Wendtii is under the driftwood, spiralis is taking over the top.
Tanks specs (since it's show and tell):
10g tank running two baffled HOB filters
Eco-complete substrate with root tabs
Finnex Fugeray 20" light
CO2 injected, weekly fertilizer added (Flourish for trace nutrients, not currently dosing macros), weekly water change
Flora: Crypt spiralis and wendtii, corkscrew vals, myrio, bacopa carolingia, dwarf hair grass, java and Christmas moss, cabomba, red ludwiga in the back where no one can see it and probably dying
Fauna: VT male (Lucky), 3 oto catfish, 2 nerite snails, ??? baby ramshorn snails