The wildcard on the identity and expression axis is expression. You can randomly choose 100 men and 100 women and each will dress, gesture and behave differently.
However, the vast majority will be monolithic in their response regarding their gender identity.
Therefore the first question to answer is "who you are you?" followed by "how do I express that identity?"
Reversing that sequence makes much less sense since expression doesn't govern identity. In other words, identity is the fixed portion and expression is the variable.
Thus identity must somehow be decided via the tandem of nature and nurture. These forces have a say in how a person develops an innate sense of self which will include gender identity and sexual orientation; in theory, both immune from attempts at conversion therapy.
For this to happen both gender identity and sexual orientation must contain elements of biological predisposition which means that neither can entirely be a product of social construct.
Only expression is the true social construct since people can wear or behave as they desire while their core identity remains unchangeable.

.jpg)