checking…
One set for the whole board, so a card in Doing means the same thing on every project. Renaming one renames it everywhere; a column with cards in it cannot be removed until they are moved.
All three off for somebody new, so a person is invisible to the invite picker until you say otherwise. may be invited lets others put them on a project, may invite lets them put others on one, and may start lets them open one of their own.