I did some Europe 3-4 days, lots of DSS 6 days on the ER.
I roll with a 22 inch, a "cube" bag from LW, and a lunchbox that I use as my flight deck bag. I also have a CPAP, so that in summer or shorter trips gets put in the 22, but on longer trips (or if bags going below) comes out and hangs off the back of the roller.
Some of this, as strange as many would believe, depends on your size.. Someone who is 5'6" with size 8 shoes is going to have an easier time packing in a 22 and nothing else than me at 6'5" with size 17 shoes. My clothes are physically much bigger. I have a friend who brings 2 pairs of shoes plus more clothes and it fits.. He's also basically a small footed hobbit.
I basically bring enough underwear, socks and Tshirts for one fresh a day, plus one spare. Uniforms is pretty much what I show up with plus one spare pant and shirt (I cannot buy off the rack).
Bringing more than my running shoes on top of work shoes is just not happening. Takes up too much room.
Winter Domestic or short call reserve is harder for me to pack for than Intl.. Because in the same reserve block I've gone to MSP in February followed by SFO, then AUA.