Hey there, welcome.
I will answer this question from an extremely subjective point of view; mine
I obviously (my own story may shed some light on the direction I am coming from), would always say that poly relationships are about and live through love, openness, honesty and respect. Have been in a monogamous marriage, have been really afraid of telling my partner or confronting my family /our surrounding and still decided that this was the only path to take. It went more or less great, we achieved a stable place and I believe that this is due to the way we/I choose to get there.
Just because you are afraid and just because there is an easier way out (btw I don't think that it is easier to lie to your spouse or family about who you are and what you do) doesn't mean that this is any justification to go down such a path. Again solely my point of view but I always question someones motives and feelings when he/she is able to cheat on a partner, break the partner's trust and still claims to be so in love with him/her. I miss love and respect in every situation where cheating is involved.
This may sound simple, but I am the person I am. If I decide to hide who I am and feel more comfortable that way, fine. If I decide that I will live up to my standards and my true feelings and desires, fine as well. I would have felt like cheating my partner just by pretending to be someone I am de facto not. Therefore I couldn't live with your B option at all. There are people out there who can. I won't judge them as far as they aren't involved with me and don't ask for my opinion. If that choice is valid for them, fine again. But I personally would never accept such behaviour in my direct surrounding when I am involved.
Without those core values (as you said in the beginning) poly isn't poly in my book.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.