I think the bag would be fine and you can always use a backpack if you need to carry some extra things from time to time.

The bikes are all nice and should be more than fine.

The only consideration you might want to be comfortable with, is the difference between the geometry of the three you are looking at.

The Soho has the seat roughly level with the bars, which will place you in a lean forward position.

The Commuter 4 has the bars slightly higher than the seat which will put you in a more upright position.

The Detour City will place you in a much more upright riding position with most of your weight on the saddle.

There are various pros and cons to each riding position so you should definitely try each before you decide.
You could also check out the used market (graiglist etc) rather than going new.