Wearable and Cast are often missed APIs. Contacts and Calendar sync is also not implemented yet. I can't think of any app that I personally used that doesn't work. That includes Google Maps and the Play Store. There were some crashes in the past, but microG became a lot more stable since then. However, I completely rely on my own infrastructure for mail and contacts / calendar sync (using DAVdroid).

Permission Google Maps has in addition to HERE WeGo:

[Device & app history] retrieve running apps

[Identity] add or remove accounts

[Contacts] modify your contacts

[Phone] directly call phone numbers [Phone] write call log

[Microphone] record audio

[Other] download files without notification

[Other] view configured accounts*

[Other] send sticky broadcast

[Other] disable your screen lock

[Other] measure app storage space

[Other] control Near Field Communication

[Other] read sync settings

[Other] run at startup

[Other] use accounts on the device

[Other] toggle sync on and off

[Other] read Google service configuration

Permission HERE WeGo has in addition to Google Maps:

[Identity] read your own contact card

[SMS] send SMS messages

[Other] pair with Bluetooth devices

[Other] access Bluetooth settings

[Other] change network connectivity

[Other] uninstall shortcuts