Theoretically of course, I would think defining threat situations as short range in public, short range at home, medium range, long range.
Pistol for concealed carry.
12 ga shotgun for short range at home
AR-15 for medium range
.308 for long range
Pistol is also the backup for the long guns if that ever becomes necessary.
Specific models would be dealer choice.
Good list, were I not so afraid of firearms.
bkmk