Hex tanks are really hard to scape. The best ones I have seen use tall driftwood in the middle with plants attached to it. Maybe some vals or other tall thin plants in the back, with anubias and/or moss on the driftwood. I have also seen one with a tall larger plant like a sword in the middle, surrounded by smaller plants.
I actually have a hex that I am planning on making a DIY background for to cover the 2 or 3 sections in the back. I have been planning it for about 2 years now, though I have yet to do anything about it. Too many other tanks to mess with at the moment.
Stocking is up to you, just keep in mind that hex tanks usually have a lower stocking limit than rectangular ones due to their shape, though this wouldn't be as much of an issue with real small fish like endlers.