I am back to report that, after reading your replies, Reach4, jadnashua & wjcandee, I called the Toto tech people and also spent some time talking to them. The Toto guy was very nice, and he thought that my toilet was already roughed in at 10" on a 12" b/c it was sitting too far from the wall. However, he thought it would work, and suggested the 10" unifit as a back-up.
I talked to my plumber & he came over to check it out. He said it was a 12", but the tank was 2" shallower than it was supposed to be. Like I said, almost everything about that ProFlo was a hot mess. So, I went ahead & ordered the Soiree, and the 10" unifit adapter, just to be on the safe side.
He installed it today, and as it turned out, the 12" was fine and I still have space between the back of the toilet and the pipes. The valve was fine, too, although the edge of the base of the toilet pushes the bottom collar of the valve up a bit, but it is still level.
As I have learned with old houses, the thing you think is going to be the problem usually never is...it usually turns out to be some other random, unforeseen thing. In this case, everything fit fine, but when my plumber had to drill into the tile for the extra 2 bolts, the tile was so hard that it was almost impossible for him to get through, and he had to use several different bits and a hammer & chisel to break it.
So, thank you so much for your advice and support. The Soiree looks great, and hopefully will live up to the hype on its flushing performance.
jbf, good luck with your situation. I hope it works.