Question about best practice using 2 phones

Hey everyone. I currently have 2 device i wish to use. I was using solely a Pixel 8a running grapheneOS but ran into issues with android auto (Disconnects and Audio skipping, tried everything online, still bugging me). So i pulled out my Samsung galaxy a56 to use for android auto, and other data harvesting apps.

My question is, What would be the best way to use these devices together?

I have 1 esim currently in the Pixel. And i am hotspotting my a56 for use of Android Auto. I am not sure that this would be the best.

Ideally I want calls, texts etc through my Pixel so it gets the sim card, however, the apps i use to communicate like Messenger and WhatsApp are on my a56 without a sim. Which makes me a little uncomfortable as they'd be better off on the pixel with Graphene yeah?

So does my A56 stay as android auto device? Or do i use it as a glorified hotspot and use the sandboxing on Grapheneos to manage my privacy?

I use VPNs on both too. Its just Google Play Services i wish to avoid.