Ortlieb is expensive as hell but extremely thick, waterproof (resistant?) fabric. I have just a bike bag Urban Roller Plus I think. It is a nice fabric texture instead of smooth dry-packish and it has a nice insert to organize everything and protect my laptop.
My girlfriend has the Various which you can flip the cover over to switch between backpack and bike bag and it is awesome, but more expensive.
Fjallraven is also good, but the strap padding wears out rather quickly. Every teenage girl in Belgium had a Fjallraven pack back when they were in style and every one has the strap pads completely flattened and useless lol.
Dutch company Newlooxs has a couple bike and backpack switchers. The material is thin though and mine ripped open on a fall during my commute.