I don not considered goose neck better nor easier then a 5th wheel, I think that is completely subjective based on users preference. I find goose necks a PITA compared to hitching up any 5th wheel.
adapated hitch hitches. You have the B&W companion which is a hitch that will fit into the B&W squalre box of their turnover ball. There is the Curt X5 which is a standard rail plate to adapt either a square or circular goose neck mount to a 5th wheel standar rail system that you can drop any industry standard rail based 5th wheel into.
And of course as you have seen you can change the king pin over to a goose neck.