As themes contain dynamic files such as PHP and PHTML templates you will need to refresh the page, it isn't as simple as just changing a theme at a certain breakpoint.
Because of this my understanding is you'll need to refresh the page, also I'm not sure why you need that plugin when Magento 2 comes with the functionality to load different themes based on user agent.
Match media solution
The closest thing to this I can see without making huge customisations is to use match media to reload the page at certain breakpoints. For example if the user resizes their window to 767px you can refresh the page. I wouldn't recommend this as it's poor UX, imagine if you was the user and you only wanted to resize the browser to compare two products in two windows and the page refreshed, you'd be like "WTF?!". IMO the negatives outweigh the positives for the few users who will actually resize the window.
Rather than changing themes I would recommend creating a responsive theme that will look correct on any device.
A brief example on how I would attempt to refresh the page for different breakpoints:
mediaCheck({
media: '(min-width: 768px)',
// Switch to Desktop Version
entry: function () {
window.location.reload(true);
},
// Switch to Mobile Version
exit: function () {
window.location.reload(true);
}
});
The boolean in reload();
is to bypass the cache as we're loading dynamic files.
Again, I advise building a responsive theme rather than doing this.