I have the back roller classic which has around two times the volume as those you're looking at and has a more functional appearance. I tend to over pack but that could be the nature of the bag. When I commuted with a laptop I routinely carried: laptop, charger, shirt, rain pants, bike lock, similar amount of bike repair stuff that you've listed, food, water, towel and sometimes shoes. I still had room. I think if you packed well those bags could work but like another person said, there's little negatives to having a larger pannier. It's also nice when I need to stop by the store and grab some stuff. The only critique of the classic back roller is the straps, out of the box they aren't comfortable (too thin, not enough padding) but this is easily remedied with a softer, more plush pad.
I just use a cheap Planet Bike rack. Has worked fine for commuting.