In my partly English-speaking country, it's unusual but unremarkable. I've never seen the
Margot or the
Margaux (ouch!) versions here - people stick to
Margot and have no problem with the pronunciation. I rather like it - might consider it as a mn instead of the longer
Margaret. And it's much fresher than
Megan.
Is
Margaux used as a human name in
France? I find it hard to imagine.