Recommendation for panniers used off the bike a lot
You might consider:


Arkel Bug, which works as a backpack. Quite modern, sporty look.
Ortlieb Downtown, which has a comfortable shoulder strap.


You might check other products of those two producers, if you need a bigger/smaller cargo capacity.

Both of these panniers are very easy to attach to your bike. Perfect for your daily commuting needs and running errands.