Along @PeterHanes’s excellent questions:
If you satisfy those questions, build out the rest of your rack on ModularGrid. Plan a whole vision and execute it; don’t be swayed by impulse (new releases often come with exciting demos, but do they deviate from what you want to get out of your modular setup?). Think of some general questions: Do you want knob-per-function things, or are you okay with menus or tiered functions? How do you want to interact with your rack (is it performative or just something playing a drone or sequence in the background)? Etc.
Once you have a rack laid out, sleep on it. For like a week, at least. If you come back to it, and it still makes sense and excites you, then follow through and begin building it. Don’t rush into anything.