The deck isn't cantilevered at all: its supported by the house on one side and the perimiter posts on the other. The plan doesn't acually show how large the upper level deck is, but it does look comfortable. The surface of a deck over an enclosed space is usually pitched slightly, enough that the water rolls off, not so much that a glass tips over. Typically a few inches in 12 feet. There are several ways of doing this. Sometimes you see a regular 2x6 deck built over a low pitched roof, but more often the roof and deck are the same material similar to the asphault used on flat roofed structures. A cool new option is LockDry, an aluminum surface that you walk on, but interlocks in a way to channel off water. A certain amount of care must be taken with flashing, siding etc. so that water can't inflitrate, but your builder won't have to invent the wheel, here: the procedures are well established. Just make sure your guy know and follows them: he'll probably tell you it won't be a problem, but ask how many such structures he's done. Still, a certain amount of all this will depend on your area [more care has to be taken in Seattle than Phoenix], and the exposure of the deck [A south or west exposure will dry more quickly, lowering chances of mold, etc]. But if proper practices are followed, you can have a large deck on the north side of a Seattle home. Here is a link that might be useful: LockDry

We built a paver patio as a DIY project. It is a lot of physical work but the result speaks for itself. The most important part is to create a good stone base which has been compacted to eliminate settling. Your best resource would from patio books like are available at Home Centers for a few $'s. If you want a deck too, place your footings as part of the patio, then build the deck. I've not used composiste decking however I know there are special screws to eliminate the "mushrooming" you mention. If you look at the linked photos, you will see that we have an egress porch (deck) from the house onto the patio. Good luck. Here is a link that might be useful: Our Patio

Beverly- thank you for the feedback. I agree the red brick does not really remind anyone of a Florida lake front house. Although we do like a good brick home (in-laws are from GA) not sure its a style fit. The previous owner was the couple that had the house built in '61 and she loved this style brick. We main issue is going to be how to handle the roof. We have some meetings coming up with architects, etc. The area that is the deck now would be the best area for the a roof but trying to keep it high enough and tie into a valley will be a fun challenge. We will likely end up with a version of a flat/shed roof with a skylight(s). On the extended area of the deck, we are debating stepping down and adding in a fire pit with seating. Not sure yet on stepping down vs. keeping it all level.

I prefer option (b) too as ours is similar though we only use the deck as transition onto the patio. Steps are landing style making it easy for seniors to use and safer for carrying foid/beverages. Our grilling and firepit are a safe distance from the house, natural gas. Here’s a video of the space. A hot tub once sat where the bistro table is now. https://youtu.be/H5t9G-Gujqw