> My biggest question is which makes/models can have the surveillance anti-features disabled by unplugging a specific module or two, while losing as little legitimate functionality as possible.

Onstar usually lives in a box that can be physically disconnected. That'll keep them from spying on you/your car even if you've never activated or used their service. I never enable bluetooth on my phone, but my car still has an AUX port and I'll plug my phone into that. If I charge my phone by plugging it into the car's USB ports I use a data blocker.