My anarchis is growing like a weed in my 80* water as well.
I myself wouldnt suggest pellia, its REALLY messy, i bought some by accident and HATE it. everyones preferances are different though.
Frogbit is great, grows like a weed as well in my tanks.
In my low light tanks I have -- rotala, aquatic banana, java fern, java moss, money wort, anubias nana, amazon sword, anarchis, some kind of Val, cabomba, water wisteria, water sprite, giant hornwort, morimo moss ball, and some other plants that I cant identify. They are all thriving! The rotala I might not recommend as it doesn't root very well (in my case) so some peices become un-wedged on occasion from fish swimming into it. But its a slow grower so it'd be great for a 10 gallon if you want low maintenence.
I find that my girls in the sorority tank love to rest on the banana and amazon swords. The swords would probably out grow your tank but you could always find a smaller variation.
For low light there isnt much choice in colorful ones, tiger lotus could work? I find that all the different shades of green make it colorful enough, also driftwood and other hard-scape decorations add color in as well.
I dont know anything about the substrate so I cant help you there, sorry!