Umm.... patience young jedi. It appears that you have more money than patience. Perhaps we could work out a trade?
Those are all reasonable choices, as far as I can see. Whether you get Cascade SS vs. Storm G4 is not going to make a lot of difference in your overclock, I think.
The pumps I don't know much about. I use the MCP-650/D4 pump.
Rad... I use a heatercore in one system (a home-made case) and a DangerDen 3-fan rad for the other.
Tubing should be fine for either choice. Tygon might be a bit more flexible, but it's going to be hard to tell.
GPU block for an X850XT? I have no idea. Send me a card to use, and I'll find a block for it.
As for the case, I can't answer that easily. I made my own 24" cube because I didn't like the cases out there (and I like making things).