Is ECC worth it for a home NAS

For a filesystem that checksums data, ECC protects the one place checksums cannot: memory between verification and write. It is not mandatory, and the honest framing is insurance whose premium is a slightly more expensive board.

Look at TBW rather than sequential speed. A consumer drive rated at 300 TBW dies years earlier than one rated at 1200 under the same load, and the fast numbers on the box describe bursts to cache, not sustained writes.