Source: I’ve been an embedded sw engineer for 10+ years

This seems like a pretty decent resource generally speaking. I’ll add this caveat though.

If your threat model includes anyone with large state level resources, you should stay very far away from anything with a radio in it. Wifi, Bluetooth, NFC, whatever, it doesn’t matter. It is possible for it to be compromised at a silicon level, which means you can never be sure it is fully secure.

You have to assume that anything transmitted via RF of any type is capable of being collected and compromised.

All that said, if your concern actually does include people with black helicopters, you already know this, and if it doesn’t, just remember that these technologies are getting cheaper and more ubiquitous all the time (see stingray), so be careful.