This is my standard setup, for both every day riding, grocery shopping and touring:

https://bike.bikegremlin.com/8229/backpack-panniers/

Backpack is the "default", with one, or two panniers being added as needed.
The backpack I use now is rather large (40 litres I think, was custom built with provided dimensions and brackets, so don't know the exact capacity in litres, just the space ).