First of all, what you need for lights is governed primarily by state laws, though the federal safety regs have some basics. That's part of the reason you get varying opinions.
Often you don't need lights on the vehicle itself if the coach lights are adequately visible while towing, but who wants to get into a debate with a LEO or court judge about that? Better to have lights active on the back of the towed vehicle and avoid any issue.
A 4-pin connector is all that is needed for stop/tail/turn EXCEPT maybe on cars that have separate stop & turn signal bulbs. If you want to use the car's own lights and they are separate, you need six wires instead of 4.
Probably the simplest way to get lights is a portable light kit, usually a magnetic mount. You can make a different mount if you like, or even set a light bar in the rear window if visibility is OK like that. Here is a basic one from Harbor Freight:
12 Volt Magnetic Towing Light Kit
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL