Default Smart Object Option for Pasted Web Images in Photoshop

There has to be consistent rules for the behavior. The source of the image cannot be a consideration. You can drag and drop, which will always create a smart object - but there's a snag here too. From a web browser, you don't get the original image, but a "proxy" from the browser's cache. In effect, a screenshot; and untagged at that.

Smart objects honor physical print sizes, not pixel dimensions. That in turn means there needs to be a clearly defined ppi value (to determine the size) which you normally don't have on the web. Ppi isn't used on screen/web.

The point is that if there is any ppi discrepancy, the image is scaled, and thus already degraded. With the different ways browsers handle 4K screens vs. standard screens - scaling or no scaling - this is an equation with several unknowns.

It's much safer to just paste as pixels. Then you know you get the maximum possible quality.

Then, once the image is safely in Photoshop, you can convert it to a smart object for further work. If you assign a custom shortcut to "convert to smart object", that's as fast as anything. I use ctrl+B for that, and shift+ctrl+B to rasterize.