Yeah, in PA the hunting regs say 3 rounds, but that's ONLY for hunting. Some clerks don't know anything more than what they need to advise you for hunting uses.
The way I see it, there are three kinds of civilian tactical shotguns:
1. Semi auto
2. Light and compact pump
3. Big and beastly buttstroker pump
1. Semi-autos are neither light nor legal to have with a P-grip and more than 5 rounds. Neither can they use varied loads. Only reason for them is rapid fire capability, and you don't even get that pump action sound that deters many an intruder.
2. If you want light and compact, Mossberg 500 with a barrel flush with the magazine is the best bet period. I'm not too familiar with the related Maverick, but it's similar. CDNN also has trade in Remington 870s for $150 and new Mossberg 500s for $200 dealer cost. For compact storage, folding stock is a good idea, I'd rather have that than sole pistol grip, but in some cases sole grip is fine.
3. My Mossberg 590 with heat shield. It has a bayonet lug and a full standard stock. It's NOT light and NOT compact. It holds 8 shots in the tube and one in the pipe if I so desire. And if I were to run out of ammo or have to go hand to hand, it's better than anything in my collection except C&Rs, which are all a little big for indoor use anyway, as well having way too much penetration.
Maybe you can merge two of these three, but I have a feeling it would be better to go with one of them.