Is mobile based on media query and can large tablets be treated differently from small phones?

[owldown]

I use Obsidian on a 27-inch 5k iMac, a 12.9 inch iPad (in landscape orientation), and an iPhone. The iPad and iPhone are both "mobile", but are very different in size and therefore different in terms of what theme would be best. I'd like some way to tell the plug-in "hey actually my iPad is big enough that I'd like to use the same theme that's on the desktop and only the phone should have the alternate theme". I'm not sure if this plugin is detecting mobile based on screen-size or some flag in the app itself, so I don't yet have an idea for implementing this.

Even more advanced, I'd like to have to way of choosing three themes, one for desktop, one for iPad, and one for iPhone.