Most video projects that fail did not fail because the video was bad.
Nothing video-related should download before a shopper indicates interest — that single rule covers most of the problem.
A poster image with explicit width and height prevents the layout shift that costs you a Core Web Vital.
Video apps frequently load their runtime on pages with no video at all, which is weight paid for nothing.
Measure before and after on a real phone, because a video test that also slowed the page has told you nothing.
It does if the video loads with the page. Done properly — a lightweight poster image, with the player and video file fetched only when someone interacts — the cost is small.
The full guide has the formats, the deadlines and the worked examples.