I've got high-light recommended stems happily growing in low/medium light, no c02. Do they show the full potential of their color? Nope. But they're still very nice plants and this way I'm able to keep some relatively hard to find plants on hand until I *am* ready to set up a high tech tank.
My hygro sunset under c02/high light/ferts would have a bushier growth pattern, larger leaves, and brilliant pinks. Under my med light/med ferts set up the leaves are a little smaller, the sections between nodes are longer and the pink is diminished to a light blush on the upper half of the plant. Still a good looking plant that I'm able to regularly harvest clippings from.
My baby tears carpet (nearing 75% coverage after 2+months) doesn't get as much horizontal growth as it would hi-tech, but I'm willing to wait it out. Hi-tech I'd be pruning and tossing the clippings. Low tech I'm pruning and re-planting the clippings.