No Google Maps or Android Auto on my phones, so I don't care much about privileged access - they have none anyway.
No, microG is definitely not talking to Google all the time, NetGuard would warn me if it did. I would assume it is not even running when I disable it (which is easily done, as opposed to stopping Google Services in GrapheneOS) - but to be fair I didn't actually validate that.
I kind of like GrapheneOS otherwise, this is by far my biggest gripe. I can even survive the icons. But avoiding Google (and other big tech) is the reason I am not on a cheaper and more convenient phone with regular Android, so if GrapheneOS refuses to support an alternative to Google Play Services, I'm not too happy about it. If there are real problems with microG then I'm sure the authors would be interested in a better solution too.