Power (qudrah) concerns the capacity to bring about or not bring about a possible thing. Will (irādah) concerns the specification of its particular time, mode or extent. Takwīn concerns its origination in existence.
A possible thing could exist at several times. Its possibility relates to power; its occurrence at one specified time relates to will; its actual being brought into existence is described through takwīn.
This is a conceptual distinction for analysis, not a claim of successive human-style acts or multiple agents within God. The dispute is whether the last meaning requires a distinct attribute or is sufficiently accounted for by power and will.