This is the thread from Reef Central where we all started and it talks about the floaters: Reef Central DIY Stand
I was going to try to explain what everything was for, but I do not want to take the wind out of Biscuit's sails because this is one heckuva awesome looking stand. All your questions and more are answered in detail on the ReefCentral thread and I am sure Biscuit could offer up his info too.
Once question to Biscuit, are the switches controlling each outlet they are connected to? Meaning the switch would turn off their respective output? Also, do you think one GFCI is enough? I wired three of them for my last project (two for lights, one for heater and pump) because I did not want a single point of failure. Do you think this was overkill?
Where did you get your plywood and did you buy a 4x8 sheet for the 1/2" and 1/4" oak? I cannot seem to find any good plywood at the local Home Depots or Lowes. May have to go to a lumber yard.
Kudos to you man, you are my hero!