I disagree that "there is no shch thing as entitlements." They do exist, they simply have no power. For example Clan Donnell consists of me and my daughter. As Clan Chiefton I have made Stillwater'd shadow tartan officially "Donnell." Can I fine you for wearing it? No. Am I "entitled" Yes. Does it mean anything? Nope.

As far as mixing well... I would not wear a McCoy tartan kilt with a Hatfield hose, they would clash. ;)