A couple of things to consider if your going carpet vs sand.
Most carpet type plants require strong light. That means you'll be pushing alot of light to the bottom of the tank to keep the carpet happy. When you do this it's a tougher balancing act to keep algae away. Using lower light plants on the rocks and spiderwood like buce, anubias, ferns and moss is much easier without a carpet to worry about. So managing light and keeping the tank "uber clean" is very important with the stronger light.
The downside to sand is it shows everything and critters can mix the two substrates together so it's important to have a good barrier of rocks or other means to keep the two apart.
I messed with the next design to move the beach to the right front. It's just not in the cards for this tank. I don't trust my design abilities to strike the right balance. At least that makes a decision and I can move forward.
I do think I am going to add just a bit more stone. I broke down one of the bigger rocks I wasn't going to use into smaller chunks to use for the beach bulkheading. I won't be doing that now, but the pieces do look nice and I think can add some nice structure to the design (until they're covered with plants at least). I have all of the ones I plan on using soaking in a bucket now to get the sediment off of them. It's crazy how pink/rose colored some of these turned when cleaned up and wet.
Lighting will be a Fluval Plant 3.0 suspended about a foot over the tank
I will be running CO2
I want to do RO water (TBD
pending a chat with my plumber) and amend as needed
I am looking to put a Wild Type Betta Imbellis in there with a few other fish eventually (pending temperament), although that could change to another arrangement. They won't go in until I get the planting settled and everything stabilized, but that does mean I am looking at plants that will do OK in Betta water temp (78F).
Given that, I need to pick plants that will work for the environment, are available and that I am capable of maintaining (read beginner or intermediate at most.)