How can they be referred to as "Thoroughly modern Royals"?
Never mind Royal, they aren't even "modern". What's modern about a practically middle aged woman clinging onto her husband's hand at work? I know I drone on about this but it is a particular bugbear of mine. But that's because I worked with my DH (same organisation, different disciplines) and we managed to keep our hands off each other whilst at work, so I know it can be done.
Re the Feud, I think it's between William and Harry, with the main grudge being on William's side. It may have started with a row over unwanted brotherly advice but it's escalated into much more than that. The greeting between them at the Commonwealth Day Service highlighted that William was much less willing to engage than Harry.
Kate is following William"s lead. There may be no feud between her and Meghan but there's no warmth either. She will behave impeccably whatever she's required to do, but it will be with her guard very much up.