If GrapheneOS doesn’t look like it will meet your needs, LineageOS w/microG may be best for you.
The main issue is that the learning curve is higher to get it to a state that’s a balance between security and privacy. You have to learn how to install it for your device, set up root with Magisk or the like, install modules that allow your device to pass/bypass google’s SafetyNet Device Assestation, install the module to avoid connecting to google via GPS, set up AdAway, AFWall, Blocker, LSPosed if needed, and get android auto set up if needed. That’s not even including all the device-specific tweaks you’ll end up needing/wanting, or how to manage updates. It’s a lot of work, but in the end you get a phone that acts like a computer you control instead of an “appliance” that works against you.
Not exactly, no. For instance, I don’t use the Google Play store (i use Aurora Store instead), but I have gotten Android Auto working on my phone. What Google features you’ll be able to get working also depend on the device and android version.