I like two separate panniers instead of two joined together. I like that if I only need one, I only have to take one. It also makes it easier to put them on the rack and take them off again.
I too didn't want anything too large, so I use
touring panniers designed for the front, even though I hang them on the rear rack. They're smaller than touring panniers designed for the back. I get four shirts and a pair of jeans in one, the week's worth of lunches in plastic containers, apples, oranges and snacks in the other. With room for a hardcover novel in each (an occupational hazard), my lock and assorted sundries.
+1 on separates, and using fronts on the back. I run an ancient pair of Cannondale fronts that I picked up for a song on Craigslist. They aren't anywhere near waterproof but I line them each with a large kitchen bag and have never gotten anything wet yet.
I keep tools, spare tube and my lunch on the right and my clothing on the left, with room to spare in each. Though I don't need it I have a handlebar bag that I use for my easy reach stuff. Having a little cargo carrying capacity to spare is not a bad thing IMO.
Winter is coming.