I admittedly don't have a Nest, but I've encountered extremely few limitations in my day-to-day usage of GSuite as my sole google account. The only one I can think of from the top of my head is, asking "ok google, when is my next meeting" gives me an error about gsuite not being supported (yet).
- No Google Play reviews
- No Google One (can't share storage with family)
- No Google Drive->Photos sync (They have completely removed this feature now)
- A few other limitations I can't remember. I switched to a regular Google account now.