It's a new-ish project FYI. But to answer your questions:

- Apps: It's Linux (like desktop or server), but "image-based" so you install apps in containers like iOS or Android do (and therefore OS updates basically-never break). https://flathub.org is generally the main app store for Linux containerized phone apps.

- Screenshots: It'll look the same as other Linux-on-phones, so like https://en.wikipedia.org/wiki/PostmarketOS for instance. It's just built differently.