[Android Head-Units] RPG0:
Just posted the same on reddit:

Gonna be a long read, with many tips

So, I have an Android headunit and was using the built-in Carplay app Zlink. Now I'm using Carlinkit dongle for Carplay, and here's why.

I'm referring to Carlinkit wireless carplay dongle, not Carlinkit wired to wireless adapter - very important!

As you already know, using Carplay in Android headunits generally introduces some audio lag, especially on wireless carplay. For example it takes some time after you press "next song" until the current song stops and the next one starts. Same with pause. Especially with wireless Carplay.The biggest issue for me is during phone calls, when you ask a question, takes a while to get an answer, and you also end up talking over eachother.

This is what I did: In the recent versions of Autokit with a recent version of the box firmware there is an advanced option to route audio through car bluetooth instead of through box. (not sure exactly what version you need, but latest versions have this option)If you select this, you need to connect your phone to the headunit bluetooth also, not only to autokit's box bluetooth (you connect to box BT for wireless)

Doing this allows for all audio to go through headunit's bluetooth which is basically lag-free.

So my setup is like this:

Wired: phone is connected by USB to dongle, and by BT to unitWireless: phone connects to box BT then to box WiFi for Carplay, and meanwhile also connects to head unit's BT for audio.

Advantages:

- No more lag when switching music or making calls, even in wireless carplay mode

- When the unit detects a call, it might do something smart that you want. Mine has a different volume for in-call, so I can now have louder phone calls without manually changing volume :D

- Since the phone is playing music over the BT connection, the unit is now aware that music is playing and knows artist and track name and it might display it somewhere, maybe have an overlay when changing tracks. Might be nice if you switch outside Carplay to some other screen/app on the unit.

- No more lag

- If unit has proper echo cancellation, it should work better, as BT is better controlled by the unit, unlike Carplay solutions which can have various delays that the unit cannot counter easily.

- If you were using built-in Carplay before (like I was), you wouldn't be able to use wireless Carplay and have internet from a hotspot, since unit's wifi was busy. If you switch to using Carlinkit dongle with Autokit, you free up unit's wifi and can now use a hotspot.

- Did I mention no more lag? :)

Disadvantages:

- Seems to use more battery when in wireless carplay mode, I think BT is less power efficient. My unit has BT 4.0, if yours has BT 5.0 maybe this would be better.

- This is a minor annoyance, but if your headunit BT is slow to connect to the phone (mine is) and you start playing music as soon as you have Carplay working (or have autoplay enabled), you might have music coming out of the phone speaker(s) for a few seconds, until unit BT connects and music goes to BT.

Beware the following:

- When using BT to listen to music, the volume on the phone matters, so make sure to turn it up to max. This volume level will be saved separately from usual phone volume though, so it's not a problem.

- Latest version of Autokit didn't find box updates for me, so if this option is not in the advanced settings, you might need to revert to an older version and use that to update box, then update app.

- After making this setup and trying to make a call, you might not hear anything, as the phone might use the carplay connection instead of the bluetooth connection. Just switch output from the phone "audio" button, and it seems to remember it for next times.

- Depending on the headunit and the software, when you get a call with this setup, headunit might decide to switch to it's own bluetooth phone app or just show an overlay. If it switches and it bothers you, try to find a solution specific to your unit. If it's an overlay and you want to remove it, what worked for me was going into android settings for app permissions and removing permission to draw over other apps for the unit's bluetooth app.