Here's a comment from the creator with a host of things that are mostly not available in Chrome:

There's a huge list of things Polypane emulates beyond the screen size.

For devices:

  - user agent
  - reported platform
  - device pixel ratio
  - rendering mode (mobile rendering and desktop rendering respond differently depending on your viewport meta tag)
  - default input device
  - orientation APIs

Beyond that it can also emulate reading direction, page language, browser locale, user-configured default font-size, different network settings and a whole range of different media queries like color-scheme, reduced-motion reduced-data, reduced-transparency, prefers-contrast, forced-colors (windows high contrast mode) and color gamut. I'll be adding even more device browser-specific emulations later this year.

But chrome already supports all of that?

I don’t know chrome devtools enough to say whether or not it already has all of these features. I will say that you can place a nail with a hammer, but if you’re building houses for a living, it might be best to invest in a nail gun.