I believe that within each person exists a range of emotions. Men and women each feel these same emotions, but it is culture that determines which of these are "appropriate" to express. The expression of these emotions are generally encouraged to be expressed along binary lines (men = hard and pragmatic & women = "soft" & "nurturing"). This is the foundation for gender, which is essentially just rules for behavior that are culturally dictated for men and women. All we have when we are born is our body, the rest is culturally determined. So I would argue that virtues of femininity aren't real but are culturally constructed ideals.
Women, as a gender, have neither the power nor the privilege that men do in our society. If they did, there would be no women's movement or feminist movements. Women are not paid as much as men for the same work, their bodies are not respected politically in the same way that men's are... that is to say, their bodies and sexuality are political, and there are many more examples I could list. I am not using the term "power" to imply physical power (There are many women who could kick my butt for sure), I'm talking about social power and privilege, a very real thing.
I don't deny the reality of the trans-community, and I don't claim to understand the unimaginable hardships associated with being a transsexual person. However, gender IS a fluid spectrum as you say, so how then can someone be a trans-anything when the line between genders is so blurry to begin with? To me, trans-anything seems to reinforce a binary definition of gender.
I think we associate images and characteristics with "inherent" traits, which leads us to name those feelings that we don't associate with male-ness as female. So yes, I believe that some people may be more comfortable expressing those feminine virtues that you mentioned if they look and feel the part. It's like getting into character for a play - after all, gender is nothing but a performance anyway.