Is the primary purpose of your refugium pod production or nutrient removal?
Based on your questions, I'd guess you're doing nutrient removal. In that case, minimal sand, some basic cleanup crew guys to keep it clean. For algae, if you can find another hobbiest to get clippings from, a variety of small clippings to start with, then whatever grows fastest in your enviroment is doing the maximum nutrient removal.
Are you mixing in tank questions with the refugium question? Or are you trying to put a fish in the refugium?
Opposing light cycles can be helpful if there's alot of photosynthisis going on in your main tank. You can tell if you need to do this by testing your pH frequently over a single day. If you have really low pH just before lights on, and high just before lights off, then a reverse cycle can be good. (A small amount of swing is normal, but you need to watch that you don't go outside the tolerance range for your fish.)
24 hour lighting isn't really benificial. Plants need periods of rest too. The entire point is to make them grow out of control. For every ounce of plant you trim out, that's an ounce of nutrients you have removed from the system. Slowing the growth defeats the point. Frequent prunings also reduces the possibility of the plants breaking down and spreading thier spoors in search of less crowded spaces.