Give images a clear purpose
Choose the dimensions and crop for each placement. A full-screen image and a small card do not need the same file. Check that the layout remains stable while images load and that important text is not baked into a background.
Keep the first screen focused
The first screen should explain the page and offer a useful next step. Avoid stacking a video, several font families and multiple animated elements there. Each new dependency needs a reason to be part of the initial experience.
Measure representative pages
A short homepage is not representative of a long article or a crowded catalogue. Test a few real pages with realistic content and a constrained connection. Record the conditions so later comparisons mean something.