I would turn off image variants in a skin that's designed to be easy for a new user, and doesn't produce surprises. Invoking variants will quickly multiply the number of output image files, and balloon the size of the upload.

And all for no useful purpose. Variants are a decade-old solution to a decade-old problem. They're unnecessary today.

And all of the presets rely on the shaky WebP processor currently used in jAlbum. The promise of "better quality" is just not true. Don't believe me? Try it with images that have puffy white clouds in an otherwise clear sky. Blocky, blocky, blocky. And if you crank up the WebP Quality to improve the output, the "faster" part of it becomes a lie, instead.

Should jAlbum core allow skins to "grey-out" the variant options?

Or at least note that not all skins support them.

I turn them off in my skins, so the settings box is simply not there. The lightbox script I'm using not only doesn't know what to do with srcsets, it fails miserably when presented with them. So not just useless, but downright catastrophic.

I haven't experimented in a while, but I suspect some masonry thumbnail scripts are also horribly misled by their presence, and do very weird things.

Finally, I don't think there's any skin that actually includes responsive thumbnails. The thumbnail table layout is responsive to viewport size, but the thumbnails themselves are a fixed size (other than some minor expanding and contracting to accommodate a masonry layout). So, there's no reason to include variants for them. Using HiDPI Thumbnails at all times takes care of the double-density displays out there.