I believe virtually everyone in western culture is more free now than they ever have been before... political posturing aside and all....
I know the situation over in Afghanistan has given me great pause regarding my/our situation here, with all our "problems". I'm just thankful the worst thing I have to endure for being "myself" is a little heckling here and there. I've never felt in physical danger for the clothes I wear, and I must give credit where credit is due, and that being the system of government that has been forged in the western republican democracy.
I wear the clothes I like, there are no rioters outside, downtown isn't blown to bits, the air conditioner is running, my pantry is full of food, my roof isn't leaking, I have gainful employment.
There is much to be thankful for.
I watched that video of people falling off a plane in flight, desperate to leave that hell hole, and I felt ashamed of myself for all my ranting over the years, the things I've taken for granted.
Justice Robert H. Jackson
Rights are inter-subjective: they exist only because we agree they do. The idea of "inalienable rights" is self-contradictory, there is no God that makes everyone agree these rights exist and respect them. There are however courts and governments that can be tasked with the role of enforcing certain rights. You live in a society with norms and the government may be able to enforce certain rights (in particular property rights) but changing norms is much harder.
so for (A) yes I am freer than a large majority of the world population, but I'm not sure that freedom is absolute as long as you live with other people.
and for (B) the source (here) is a few hundred years of cultural development that means we as a society have agreed on certain rights and respect others and a government that enforces that.
To that end, we have agreed to codify a number of those rights in a constitution and (to bring it back on topic) here we have a "freedom of expression" which also covers the way you dress. So we have the situation where society has norms (e.g. that men don't wear skirts) but the norms (&laws) also say I can if I want to. The government is not tasked with changing people's norms, only with protecting my rights. If I want to wear a skirt to work there is little the employer can do about it, however they also don't want to because the norms of society are that people can wear what they like (there a some rules) and the employer understands these norms too.
To cut a long story short, the barriers to skirt wearing are not legal, nor is there a cultural taboo against it, but entirely within my head. And of course we are social creatures and are thus strongly affected by the opinions those close to us. But that is something society, constitutions and governments can't do anything about.