He is, in effect, Princess Margaret. Archie is Viscount Linley (now Earl Snowdon) and Lili is Lady Sarah
I'd say he's less than Margaret.
Margaret was the young, beautiful only sibling of a reigning queen. There was quite a long time when the only high profile adult royals were HMTQ, Margaret, Philip and the queen mother. Margaret also had a rather interesting romantic life which kept her in the headlines for decades.
By contrast, Hary is already borderline middle aged. By the time William is king, he'll likely be in his 50s or older. By that time, George and his siblings will be young adults, close to the age Margaret was when Elizabeth became queen. All the focus will be on them, not on their ageing uncle, even if he was still a full member of the royal family.
Would many of the public be able to name their DC? Or recognise pix of them? Or know what they do for a living?
In the case of Sarah's son Arthur actually, yes I would!
That's him in the pic. He works as a trainer, in case you were wondering!