txhatch, congrats on the purchase. Let us know what you think after you get them on.
As doood said, they are made with adjustable length "bodies". That is why they look the way they do. I've always wanted a setup like that but I just cheaped out and extended my upper caps for shock travel.
1. Not my question to answer.
2. I believe that they won't revalve them for you just because you order custom rate springs but I'm willing to bet that the springs they carry are still within their damping adjustment range. I actually wonder how many different rate springs Tein even carries. For some reason, I'm thinking they only have 3 different rates or something like that.
3. Because the length of the body is adjustable, the height in comparison to stock will vary and you will retain good shock travel...as long as your upper control arms or tires aren't hitting anything.
About the custom work being done to your Konis...sounds awesome. Who's doing the work? Are you changing them to be double adjustable? I really do think that if you can drive with them on the roads right now, that you can drive with them after the custom work. In fact, I can only imagine that it would be better. Chances are that they will improve rebound damping to handle your high spring rates. Compression damping won't really need to be tweaked much IMO but I'm no expert... So with proper rebound damping and more travel from being shortened, I'd imagine your handling will improve a good amount.