Who is the authority on Setting up declared areas under AFSPA and revoking AFSPA in States?

Power to declare areas to be disturbed areas.—If, in relation to any State or Union Territory to which this Act extends, the Governor of that State or the Administrator of that Union Territory of the Central Government in either case, is of the opinion that the whole or any part of such State or Union Territory, as the case may be, is in such a disturbed or dangerous condition that the use of armed forces in aid of the civil power is necessary, the Governor of that State or the Administrator of that Union Territory or the Central Government, as the case may be, may, by notification in the Official Gazette, declare the whole or such part of such State or Union Territory to be a disturbed area.

Sir my doubt is regarding the authority who 1) Whether centre/state has a veto over declaring and 2) Revoking AFSPA, because as I understand, the authority regarding invoking and revoking- both vests equally in Centre and States . And secondly- is there a need to initiate AFSPA via a statute, or could it be done with an executive order too

Act clearly says governor - that clearly means central govt with advise from state govt. AFSPA itself is a statute. Law and order is a state subject State through governor asks for centre / army support by declaring an area as affected under AFSPA.

but is the chain of command the same for "revoking" as well?

CM can advise the governor to revoke the area

so he has no "power" as such- going as per the article then?

Only the governor has the power. CM has the power to give such an advice not the power to revoke