To answer your Q... 1 on 1 with the right woman is always nice.
Adding a 2nd woman could turn it up a notch if the parties connect.
If I was with a girl who would be into it and it not create drama, then seeing her with another woman would be hot and make the encounter more intense. But, the risk of drama during or after would have be nearly non-existent, which in many cases is not realistic. So, while ideal, it may not be possible.
So, if adding a 2nd provider, I'd rather have a say in it, so between the options I gave, I'd go with D, but make sure both providers were on board with it. Or, I'd ask my first choice if she has anyone she'd like to play with us and see if I am of like mind.
In answering my own question, I understand it's not black and white. But, I've also never done this YET.
So, if I was given the choices I asked and simply had to rank them, based on assumptions that (a) the non-provider would likely be at too much of a risk for drama, (b) that I'd prefer to partake in the selection of the +1 and (c) YOLO and 3 is bucket list thing, I'd say:
C, D, A, B
Ladies and gents, please share your thoughts in response....