what should and shouldnt be ok for a v6 to tow?

I towed a 5er with a (large block) 4-cyl. OK, so it weight 1800 lbs loaded and was all of 18 ft long. But it wasn't happy with hills/grades.

But you are talking a toy-hauler. I'm not aware of any toy-hauler that is small/light enough for a V6. They tend to be large (30+ ft) and heavy (12,000+ lbs). Which puts them right out of a V6, or a small V8, or anything but a large V8, a V10 or a good strong diesel.