I think you've made a good choice in the DH. I feel the material choice is based on weight, both your physical weight and carry weight. You really don't need a double layer if your physical weight is below fabric recommendations unless you want to use a pad in between the layers. Once you are set on weight choice then decide which fabric you want. The real difference between nylon and poly is the stretch factor as both are pretty close to comfort "feel".
Same goes for all your hammock accessories, you have to figure out where you will use them and how are you going to carry them. If pack packing, light weight material and equipment is of greater benefit than carrying everything on a motorcycle (as I do) or car camping.
As for suspension, watch Shug's video's where you will learn a lot on hammocks, suspensions, tarps and "what not"
Personally I prefer the cinch buckle. It's fast, uncomplicated, dependable and easy to adjust at any moment and a no-fiddle ordeal.
Good luck. Choices are part of the fun!