We are quite reserved as well. Kisses are OK, as long as they aren't of those kind that get you out of your clothing within some seconds. Cuddling is something we do all the time and not only restricted to the couples but everyone with everyone. (Yes, the two guys are cuddling each other
Or to phrase it more precisely, Sward loves to cuddle Lin.) Holding hands, other signs of attachment and care are OK as well, none of us has a problem with that.
In my case it comes down to my personal taste. I don't like 'showing off' in a way. I am well aware of others around me and I have never been someone to display my affection in front of others. And it doesn't matter if those people are strangers, friends, family or my other partner, I am quite protective of those moments and want to enjoy them in private, just me and the partner I am experiencing them with.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.