My bike panniers will each hold a six pack very nicely. It’s a bit too precarious to fit in a 12 pack.
If you go to the LCBO, two six packs will cost you the six pack price times two.
If you go the Beer Store, their policy is two six packs will cost you a twelve pack (and two twelve packs costs same as a 24).
I think the Somerset Beer store is a fabulous place. Except … expect some long lines if you show up at 10am Monday (recycling day).