Is this too vague?
What are the physical limitations that I have to keep in mind, when writing about nanobots?
Like maximum effective speed, waste heat minimums, computation ability minimums, etc.
Should I move to Worldbuilding, or does this have enough physics content to count as a Physics question?
Yeah, I'd say it's too broad. But more than that, it's not actually about physics, so it's completely off topic for us.
Anyway, given that your concern seems to be writing about nanobots, rather than building or designing them, Worldbuilding is probably the place to start. You would have to ask them whether they consider it too broad for that site.
