The four constructions are not perfect semantic substitutes. Coordination usually names contrasting attributes or subjects; negation with exception limits a field opened by negation; innamā expresses restriction through a single established construction; and preposing shifts attention through constituent order.
“Zayd is a poet, not a writer” explicitly mentions the excluded description. “Mā Zaydun illā shāʿir” normally leaves that contrast for the context to supply. “Innamā Zaydun shāʿir” also focuses the claim but may address a different listener misconception.
The method matters: a mature analysis asks why this particular structure suits the correction the speaker is making.