The main target of the Godot Engine are game developers. But Godot's easy workflow and functional UI elements, makes it also a good fit for non-game applications. There are already some out there you may know, like Pixelorama, an Open Source 2D sprite editor.
For sure! However Godot has low processor mode that lets you control the frequency of the update when no changes are being made. That update time can even be changed from code so you can adjust it situationally.