I'm not a 2400 owner, but will take a stab at your question about the fresh tank capacity. It probably depends on the type of camping you do. Lots and lots of people hook up to fresh water when they get a site, in which case, their FW tank capacity is sort of a mute point. Personally, I always operate off of my tanks, even if W hookup is available. For one person, my 38 gallons gets me two weeks when I act conservatively. Then its no big deal to simply fill up the tank when I'm at a campground with water. Hope that helps, at least a little!
Edit: I just realized that my response may be misleading without giving you more info. I am able to go two weeks before filling up the FW tank largely because I use campground showers and drink bottled water. I am only using the FW tank for toilet flushes and dish washing. So I'm using 2g or so per day (6g is in the water heater and not counted towards the 38g total).