The Tangle, when stuffed full, sticks out about an inch on each side past the frame, for an overall width of about three inches. I haven't experienced any thigh rub, and, for reference, my thighs measure 23 inches. My bag's a size small, so it's only four inches deep; the size medium and especially the size large have more room, but whether you can fit them depends on the size of your bike. As to scuffing your frame, I couldn't really say; the attachment straps are heavy duty nylon, but I can't imagine that they'd scuff the paint on your bike, especially since the bag doesn't really move. There are six attachment straps that hold the bag pretty firmly to the frame, so while the bag is easy to mount and remove, it isn't quick; it takes a few minutes either way. If you're looking for a bag that you can easily remove and carry, the Tangle might not be the best choice, as it has no carrying handles or straps; it's really just made to stay strapped to a bike.

If you want a bag that you can take with you, and you can afford it, the Carradice quick release bag is probably your best bet. It's expensive, but I've never read anything other than glowing, enthusiastic reviews about Carradice products. Sometimes "paying for the brand" is actually worth it, if that brand produces a truly quality product that can't be found elsewhere. And it might be vanity, but some of the price disparity between Carradice bags and those seatpost mounted rack/bag combos reflects how pretty Carradice bags look, and also how ugly the lower priced alternative looks.