On the choice of toilets: get the ones that you like the looks of the best. All will work fine. There's nothing particularly "drippy" about the Aquia on refill; that seems like an odd, one-off complaint by someone. In your initial post, you were concerned about the prices, so I recommended that Vespin II, as it is the skirted version (you wanted a skirt) of one of Toto's most popular toilets at the moment, the Drake II, and is the least-expensive of the skirted toilets. In short, it's a great toilet and a great value. The Soiree is a wonderful toilet, but it's more expensive without any meaningful increase in performance. In our master bath, we have a Carlyle II, not because it works any better than a Drake II, but because we liked the way it looked, and knew it would perform as well as any of the other "II" toilets.
In short, you can't go wrong with any of your choices.
If your home has 12" rough-ins, you will not need to buy any different Unifit adapter. The skirted toilets all come with a 12" Unifit in the box, included.
A plumber will traditionally provide the wax ring when installing the toilet.
Now...where to buy. You are building so you have plenty of time to take delivery, I assume. This gives you time to shop around. Decide on what you want, then shop!! The best way to do so is to open the yellow pages to Plumbing Supply and call around to at least 7 places, regardless of whether the ad says they carry Toto, asking for a quote on a specific model number -- e.g. CST474CEFG, the Vespin II -- and a color (i.e. cotton white). Tell them you are ready to pay cash today for it, and that price is important in your decision on where to buy it. You will be shocked at how widely the prices vary from supplier to supplier. In Austin, Texas, for example, perseverence by one of our contributors found a place that routinely sells at or near the lowest prices available from any sales channel, as well as a place that sells at almost the full "suggested retail price". They are entitled to choose the price at which they are willing to sell, and you are entitled to call around and check different possible sources to get the best price. Also, do your research and know what a fair street price is for each model.
Since you are building, you can have the plumber put the supply anywhere. The spec sheet says 6" above the finished floor and 8" left of the toilet centerline. Many of the Totos will be happy with significantly-less distance from the centerline, but if you can put it anywhere, you might as well put it there.