https://www.arkel-od.com/en/bug-commuting-bag.html I have an older one (bought used), rock solid. Better attachment than Ortlieb (and that's quite good). I'm hard on pannier connectors (shattered several Timbuk2's), so no question in my mind that the Arkel would be a solid choice.

But tastes in bags are all over the map (little pockets, big space, etc.).

Ortlieb makes an adapter, letting you turn one of their bags into a backpack (I haven't used it) https://www.ortlieb.com/en/Carrying-...ll%20panniers/

Alternatively, their "urban pannier" is quite roomy and good. The strap is too narrow, but https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 is a good addition that makes it *almost* as nice to walk around with as a backpack.