I've had extraction problems with Winchester Value Pack shells in several of my 12 Ga 870's.
Ditto. It'll work fine in a loose-chambered break-action, but I have no reason to keep bulk shells around that match a particular gun. Specialized target rounds, maybe, but not bulk stuff.
"Bulk Pack" shell are the same shells you buy in smaller boxes of 25.
Negative on that. At least I've never found the same shells in other Winchester boxes. Most obviously, they have different hulls.
And while I won't ever buy Universal bulk shells again, any other Winchester ammo has been fine, and I wouldn't hesitate to use Winchester shotgun ammunition of any other type. (I happen to prefer STS to AA, but that's neither here nor there.)
At Wally World, I buy the Federals if I want inexpensive bulk ammo. Same price as the Winchester, but IMO better stuff all around. For more serious target shooting, or if I want to reload the hulls, the Remington Sport Loads are great. However, the price has climbed significantly higher than the Federal bulk shells, so I am a bit more picky about buying the Remingtons.
In my experience, Remington's hulls are the best at several price points. Highly reloadable, even the cheapest ones. However, if I'm going to toss the hulls, e.g. while hunting, I don't care. (Yes, I do try to pick up my hulls, not just leave them around in the field. But they get dirty and muddy, and I'm not fond of reloading muddy hulls when I plenty of clean ones.)