I have long seen a pack/pouch, designed to accommodate a weapon, and attached to my person, as being on-body carry, rather than being “off-body,” perhaps because my first PD-issued duty holster was a low-slung, swiveling flap holster. (Almost immediately, I switched to a better-made, PD-approved, medium-ride-ehight, alternative flap holster, made by a local shop.) I will repeat the “attached to my person” part. Obviously, when one un-slings or un-belts such a pack/pouch, it then becomes off-body, with all of the liabilities attached to that.
Access to a weapon, inside a specifically-designed pack/pouch, can be as quick as, or more quick, than some deeply-concealed, under-the-clothing carry rigs.
The Safepacker, made by The Wilderness, in Arizona, a long-time favorite, of mine, can be hand-carried, worn on a strap/sling, worn on a belt, or secured to a larger bag/pack. The Safepacker, itself, is made to accommodate a handgun, a reload or two, a few very thin/small items, and not much else. In the past, The Wilderness has made runs of portfolios and packs specifically made to accept an externally-attached Safepacker, but the Safepacker has always been made with attachment to backpacks in mind.
Concealed-carry laws can be a moving target, so I will not mention specific states as being CURRENTLY applicable, but there are, or have been, jurisdictions where concealed carry under one’s clothing was prohibited, unless one possessed a carry license/permit/privilege, but where a handgun, or other type of firearm, could be legally toted in a visible pack/pouch, without the need for the weapon, itself, to be visible. Notably, the above-mentioned Safepacker met the legal definition of “open carry,” in AZ, in a time when open carry was the only way for most private citizens to legally carry in AZ. (The AZ concealed-carry licensing system finally arrived, in the Nineties.)
I am not saying that the Safepacker, or any other bag/pack that is designed to accommodate a firearm, meets any other state’s legal definition of acceptable open carry. I must emphasize, check applicable local/state statutes.