I own a lowepro vertex, rover AW II and Photosport 200AW.
The vertex is what i store most of my gear in and take out on big all day shoots, the rover AW 2 is a nice walkabout bag, a lot more discrete and you can ride in it. I now have the photosport for carrying a camera while i ride and for that i can’t recommend it enough.
The vertex however is too cumbersome for riding, its just too large and although it has plenty of straps it doesn’t sit comfortably.
So.. for your use maybe something like the rover? It fits a amateur body + 3 lenses and a flash in the bottom with a top compartment big enough for regular riding supplies. I’ve also used a camelback bladder in one too however there is no specific routing for one so i had to adapt things a bit. I also found that when i wanted to do a long ride with a camera the padding supplied with the rover fitted nicely in my dakine bag and created a good safety wrap around a camera + lens.
If you don’t have gear and want to do longer rides with camera gear and want the best comfort in doing so then get something a little more active wear specific and go for a photosport.