I have 254fsx which is older version of the 264fs. I have the grey water system, and don't like it. It dumps the sinks, and floor drain in the head, into a box located under the ski locker, then is pumped into the waste storage tank along with the Head waste. only one tank, and Just makes you require pump outs sooner. If you don't have it, then this water will just drain to the bildge, and get pumped overboard with your bilge pump.
As for the portlight, I don't have one, or a fan. I do get an odor in their from time to time, heat not the issue for me. Bigger issue for me, is no natural light. need to turn light on every time, and my kids always forget to turn it off, draining my batteries. These boats should have a portlight option.