Do I need a tourer or can I get away with a road bike & backpack for a week away?

http://bikepack.pl/

go for them, cheaper and easier way to tour, helped keep the bike feel lively without getting bogged down by panniers and rack.

I now swear by them, Scott do too;

Bikepacking gear like that is my preferred method for carrying stuff as it doesn't add to the width of the bike, doesn't rattle about like panniers often do, and is way more stable than a lot of traditionalists would have you believe.
I've had mine fully loaded with huge saddlebag, frame bag, and handlebar harness and never once felt unstable on the bike.
There is also the added benefit of being able to use the kit on pretty much any bike whether you have rack mounts or not.

edit - here's someone else "touring" bike;