My perspective will be somewhat different from the others as I am an American (although my mother was born in Scotland and didn't come to the USA until after WWII) and not an expert in the history of the tartans.

I've attended and participated in Scottish Festivals and Highland Games here in the USA for several decades. I can say I only know a small handful of men who switch between clan tartans. Most settled on their "clan" early on and stick to the one. In my case it is Buchanan although we have Gordons and Grants in the maternal side of the family.

I'm the first to support the freedom to wear what you wish, but I would just add those observations.