I'll have to check out MacroDroid. I'm currently set up with AutoMate, however there's a few annoyances which I think need ironing out. Vanilla Android Auto might not be the most exciting, but it's certainly the most friendly for driving safety.
I leave my tablet as-is. AutoMate automatically wakes the tablet into car mode on USB power and goes to sleep when it loses that. My car (Chrysler 300C) has accessory power for 30s (I think I can increase this in the EVIC) after the ignition is turned off which keeps the charger energised, and by extension the tablet. I'm not too bothered about having to boot up the tablet if it does discharge its battery to shutdown. I think it's maybe a week or so for it to do that, likely less when the tablet ages. As long as it charges and runs on the supply happily I think we're good. In that instance, I might have to see whether an auxiliary power bank would be a workable option. Not at this stage though. Bear in mind that most modern car head units still take about the same amount of time to boot as an Android tablet anyway.
I'm having minor USB issues myself, however this is down to the cable I need not being available. A lot of USB C "charging" cables are only pinned for power and not data. This might be part of any USB C issues you might be having. I myself need a USB C male with a tight 90° or 180° turn, out to a USB C female for the hub's pigtail. I might have to make the choice to fabricobble myself a USB cable just for this purpose....
This is a photo of the install, prior to me wrapping it in 3M brushed black steel vinyl.