Make sure you actually "test ride" whatever pack you're planning to buy. I've found that (just like shorts, shoes and saddles) one cyclist's pleasure can definitely be another's pain.

As mentioned by CCrew above, the beefy waist belts featured on a lot of hiking-oriented packs are just too restrictive for comfortable biking. I rode to work for several years with a Colorado Cyclist's "store brand" pack. The belt kept my load from swaying but didn't impede leg or hip movement. Unfortunately it's no longer made.

Sounds like you've put a lot of thought into your search. I wish you well. Let us know what you eventually choose.