Not bad questions at all.
Any restore you do has to be verified by Apple's servers. But since, once 5.1 is released, they won't be signing 5.0.1 anymore, you wouldn't be able to roll back to that firmware. Just like right now...you can't roll back to 5.0, since they're no longer signing it.
I've also got my blobs saved for 5.0.1 using TU, just in case they come up with a way to circumvent the process and allow you to restore to an older firmware. It's just a good practice to get into.
And yeah, the A5 devices are different. Not exactly sure what Apple changed, but something about the way firmwares are signed is different, making the old way of downgrading firmware obsolete (at least how you did it on earlier iPhones). Again, hopefully they've figured something out, because at this point, if you "accidentally" upgrade beyond 5.0.1 and there's no jailbreak, you're screwed.