If you need to wear off one shoulder then skip the Chrome. It is only designed to be work across your chest/back bandolier style. They are great on the bike though. I wear mine without the stabilizer strap and it still stays in place even at high rpms.

Try a Baileyworks 253 Courier. I use a medium one for my carry-on bag to carry a laptop, accessories, and some clothes. It carries a surprising amount of stuff. You can wear it any which way even though you can order a left-swing or right-swing model. The strap is attached symmetrically (unlike most pro bags) so you can wear off either shoulder , you just can't access the adjusting buckle if you put it on the 'wrong' shoulder.

I was using my giant Reload Deluxe for my carry-on for a while but it is just too much bag for an everyday quick getaway type of bag. I like that I can wear the bag off one shoulder but you can't switch shoulders as the strap is attached at an angle specific for your carry.

I also use my Deuter backpacks sometimes when I don't carry very much but having the large cargo hold of a messenger bag spoils you. Especially when you need to carry awkward or oversized items or go grocery shopping. Have tried backpacks from Osprey, Mountainsmith, Gregory, Deuter, Camelbak and I prefer the Deuter ones the best for ventilation and features.

One last thing, I would resist the urge to get a too-big bag. I kept getting bigger bags until I found myself with a Chrome Kremlin and realized that I was never going to (nor would I want to) carry as much stuff as that bag is capable of (I once fit a wheel in it with room to spare). As it is my Reload Deluxe is a little too big and I only use it on the bike and only when I have to.