In the current state it draws into a pixel buffer array which you can then display on for example an epaper display connected to a Raspi or other embedded device.
1. No. Neither. It does all the drawing on its own. Right now even fonts.
2. I think he would like to make it platform agnostic that way (i.e. provide reusable parts), but no, not right now.
3. His primary goal is/was driving UIs on embedded devices and AFAIK wants to complete it at least for this task.
Disclaimer: In contact with @cosmo in some Slack, due to my SwiftWebUI project (which offloads a load of things to the browser, so his stuff is quite different / more complex in many ways).