Most plants are best if not potted, in my opinion. The potted plants are largely those which were grown emersed (not under water), so they were grown in little pots for ease in "harvesting" them. Emersed grown plants very often shed their leaves when planted in an aquarium, because they have different types of leaves when they grow submersed, and need to grow a new set of them.
Stem plants are generally cuttings from growing plants, grown submersed. Those need to be separated and planted individually, not as a bunch.
I agree that the For Sale forum here is a very good source of healthy plants, usually "harvested" as they are needed to fill an order, so they tend to be very fresh. But, where the For Sale plants here used to be much cheaper than those from commercial stores, I don't see that being as true now. They are not over priced, but they also are not "steals".