Welcome to LS!
I can't answer all of your questions, but I can help you with a few of them.
Toro owns Exmark, but they are still two individual companies. They do share a lot of the same looks and features.
As for which blower- Stihl or Shindy? Both are excellent blowers regardless of what some here may try to tell you. The 802 is a true 2 stroke, while the 854 is a 4 stroke that runs on 2 stroke mix just like the Stihl 4 mixer's do. I prefer the 802 personally. It is a great blower. Easier to maintain, and much simpler in design. The BR 600M is a topnotch blower as well, and all of the big BP blowers are very close in performance.
Don't overlook Husky's new big BP's. Several of us here have them and love them.
I have a BR600M, and a Husky 570 BTS, and love them both. The Husky is a bit stronger now that it is getting broken in, but the Stihl is lighter and quieter, and better on fuel. All the big 2 strokes use plenty of fuel, but they perform like there's no tomorrow, so it's a wash.