What ratio to choose for pictures for the site?

Question

Design

I got confused with responsive images and made a full-scale implementation with intrinsic ratio, webp, pictures tag and other goodies. But now the question arose regarding the design and stood in a stupor.
What ratio to choose for pictures for the site? Ideally, this is probably done by the designer at the stage of creating the layout (as far as I understand the process) based on the overall design, but in my case there was no site layout, it was made up in the browser.
I basically have 2 kinds of images. The first one is the main picture of the article. Those. what goes at the very beginning is an illustration of the article, and the same picture is shown, for example, in a preview card. The second type of images is already illustrations in the article, for example, for each paragraph, paragraph, etc.
I googled, the most common ratios are 4:3 and 16:9. Choose between them? Which one where? My eye tells me that widescreen is probably better for the main / card, and more square in the article itself. How about in practice? I tried to look at other people's sites, but I do not see patterns. It feels like everyone is pushing whatever comes to hand.

Answer 1

Usually the opposite. Preview 4:3 in article 16:9. And it doesn't matter at all. Depends on the layout.

Answer 2

Given that images are more used as previews (do not carry a semantic load) to articles, it is more logical to choose 16 * 9, since the occupied area will be smaller and there will be more emphasis on the text itself.
But an image with a 4 * 3 or 1 * 1 format is better to use in social networks, where key information is placed just in the picture, but of course, the coverage of the screen area on smartphones is greater.