In the noun phrase "plan to do sth", "to do sth" always modifies "plan". Possible differences arise in the nuance of the word "plan", which can mean an ambition, intention or proposal, or a specific set of actions that are to be carried out, or perhaps something between the two. (1) uses the former meaning (except in an unusual intepretation).
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Hans51He has announced his plans to retire. I think that here his plans means his intention and his plans = to retire so the meaning of plan is different from a set of things to do in order to achieve something here, right?Right. It is unlikely that anyone would announce a sequence of actions to be performed in order to retire.