What actually matters for a small static site in search

Three things, in order: the title and description, the words the page uses matching the words people type, and links from places that already rank. Everything else is polish on top of those, and no amount of markup compensates when they are wrong.

It helps discovery on a new domain with no inbound links, which is exactly the situation a fresh project is in. Once pages are linked from anywhere indexed, the sitemap stops mattering much, but it costs one file to keep.