I’m not knowledgeable in the deep technical details of rocketry. But curious - how else would the first stage be operated? Should it be autonomous?

Yes. The timings involved would make it impractical to land a rocket reliably via human teleoperation even with zero latency.

I’m not a rocket scientist but my assumption is that it would be internally guided and only take external inputs in the form of GPS and “land on the ship” or “don’t land on the ship”. Saturn V was manned and had a an internal guidance computer.

No, but they want to be able to remotely abort.