Team Sunak here - at least he can afford his own wallpaper so won't personally be beholden to donors. And I cannot believe in a woman who dresses up as Margaret Thatcher, doesn't know how to pronounce Taoiseach and does incredibly bad trade deals.
As for party members having some say - highly suspect. At least the Tory party insist on a length of membership - to guard against infiltration, one would think, or ensure the Old Guard remain in power. Labour party went for mass membership with no safeguards. AFAIK.