Carter, I think each type of trip demands different kinds of packing. I travel SO MUCH that I've become a real expert -- thanks to help from people here, I might add.
My first impulse was to pack a "capsule wardrobe." But -- especially in transitional seasons -- this can be a tricky way to go, at least until you are quite practiced at it. I really benefitted in the first case from Gaylene's advice to pack for my activities. This is especially important when the activities are varied. When that is the kind of trip I am doing, I make sure (especially in transitional seasons) that I have at least one "cold weather" or "rainy weather" outfit prepared for that activity, and one "unseasonably warm" weather outfit planned for that activity.
Typically, even when you are going to be doing a lot of different activities, you'll be doing a set number of types of activity. So thinking a bit about what type of thing you'll be doing most should help you focus on the rest of the wardrobe.
Now I use a modified version. I consider the type of thing I'll be doing and make sure I have the core items for those activities. Then I "build out" a capsule from those core outfits.
For my latest trip, I simply created a fairly large capsule a la Angie. I actually looked at one of her autumn business casual capsules, I think. She'd started with a foundation of 3 bottoms, 6 tops, and 2 toppers.
I decided that for me, given the specifics of my situation, that capsule wouldn't be large enough. The temperature variation was going to be so great, and I was going to be away for so long -- my need to layer and my need for variety were going to mean I'd need more stuff. So I simply added bottoms, tops, and toppers to get to what seemed reasonable to me.
I think if I were doing a 2 week Europe trip, Angie's business casual capsule would be the right size, although I'd probably add some gear items and a few more pieces for layering. Plus extra footwear for variety.
In this case I am doing laundry. But for most of my 10 day to 2 week trips I don't. I will usually bring 3 pants, a skirt or dress, and accompanying tops/ toppers. I would wear the pants more than a couple of times. I launder undies in the sink as Parsley suggests. I often launder other things that way as well -- especially tops or jersey items. They dry overnight.