While I can't help (any more than Google can) with creating your bootable USB stick (I have yet to have a need to install from a flash drive..) I can help with the driver question.
Vail is built off of Server 2008 R2. Ideally, those are the drivers that you want to shoot for.
That said, Server 2008 R2 is a kissing cousin to Windows 7 (they're the same codebase.) So, Win7 drivers should
What Server ratings on the drivers get you is (theoretically) a better reliabilty & stabilty rating than you do with 'dekstop' drivers.
Being that you're running (or, will be running) it on an nVidia-based desktop board, you probably aren't going to find Server drivers for it. (This, BTW, is why I always
recommend that someone install WHS on an Intel-based board. And, one with integrated graphics, too. Server-rated drivers are usually a non-issue in Intel land.