I've been tasked into looking at the capabilities of PowerApps, but from what I've seen it appears the only option you have is to create an app that is designed for mobile or tablet. In other words, all the elements of an app are extremely large and designed for a touch screen, as opposed to using an app on a desktop PC or laptop.
When configuring an app, I noticed the only options I have are to switch between portrait or landscape orientation for a mobile phone. However, when I did some Googling, Microsoft's website shows the following option:

As far as I'm aware this ability to select a custom resolution (and potentially build a desktop app?) is not visible in my PowerApps. Has it been disabled? Is this how you create a desktop app? Is it possible at all?
Any help would be great, thanks.