Set aside some time early on in your project just to create a small proof of concept where you actually slap on that Textual UI. That'll inform you of what's needed later on. You don't even need to merge that proof of concept, the point is just to discover what's needed.
I've done that kind of by mistake, in that I wrote some UI screens and saw how to hook them together. But learning Textual, some Python, and object oriented Python all at once was difficult for me.
