Grace and favour homes are given at the Queens discretion.
The sovereign grant is only for working royalty. Kent's would get some income for example where Zara would not. No CC events, no money.
Andrew was shot down that as his daughter's aren't "senior royals" they couldn't get security covered, so that'll be an interesting thing to work out with others.
Charles dutchy is for the POWs family, so once William becomes POW it would go only to his family.
Grace and Favour homes are largely for the 'working royals' so the Gloucesters and the Kents other than the Michael's of Kent get a grace and favour home.
The Sovereign Grant is for the expenses the royals have so it pays for things like the salaries of their secretary. It isn't a salary to the royal for duties. They don't actually get paid to do any royal duties at all. Andrew lost his share of the Sovereign Grant because his staff was sacked. He personally didn't lose anything financially.
The Duchy of Cornwall provides the private income for the Duke of Cornwall and his family. Usually the Duke of Cornwall is also the Prince of Wales but that isn't a given e.g. 1901 the future King George V had the income of the Duchy of Cornwall from January to November but he wasn't Prince of Wales. Charles had the income of the Duchy of Cornwall from 1952 but he wasn't created Prince of Wales until 1958. (As he was a minor it was managed for him but the income was still being set aside for Charles from 6th February, 1952). What the Duke of Cornwall decides to use his money for is his business and his alone (he could, for instance, put all of this year's interest on a horse in today's Magic Millions horse race on the Gold Coast, which Zara and Mike are attending). If he wishes to continue funding Harry he is within his rights.
The monarch has the income of the Duchy of Lancaster for their personal use AND to provide allowances for those members of the family who support her or whom she wishes to support so the Duchy of Lancaster provides a living allowance to all the royals other than the Wales branch of the family and the Michael's of Kent, Beatrice and Eugenie who earn their own money from a range of sources. Charles wants a smaller royal family so he doesn't have to support so many people from this source of money but he will need to ensure that his siblings are still looked after financially - unless he wants the bad press of them ending up on the streets (He was the one who stepped in and ensure that Marina Ogilvy had somewhere to live when her parents had had enough and she was forced to go looking for a council flat).