On a small site three numbers matter more than the round score. LCP is when the main piece of the screen showed up. INP is how fast the page answers a tap. CLS is whether the layout jumps while the rest loads.
LCP
The large element on the first screen: an image or the heading. Give it width and height, do not lazy-load the hero, and do not wait on a web font for a single word. Until that font arrives, a system stack already shows the text.
INP
The page feels late when a third-party widget sits on the click: a chat, a pile of pixels, a player. Keep your own code and one form. Add an outside chat only if leads cannot be handled without it — and not on the first screen if it can wait.
CLS
An image or embed with no size pushes the text when it arrives. Reserve the space up front. The same goes for a banner inserted above the heading after paint: the person aimed at a button and it moved.
Where to read the numbers
A mobile profile, the URL that is already deployed, extensions off. A local build is almost always cheerier than production: no live compression, and it does not take the path the file takes from the server. Ship what the client opens, not a localhost report.
How a static build beats a heavy CMS on these metrics — the note on PageSpeed. What belongs on the first screen — the note on landing structure.