Just some additional notes... The delay is already quite high for wired CarPlay with the VW MIB2 audio system. Wireless CarPlay obviously adds some more milliseconds on top. The ITU recommends <150ms for one way (300ms RTT) but states that up to 400ms (800ms) is still acceptable. With the adapter we are a bit above this "limit". It is in my opinion more a problem of the system than the adapter itself.The latency issues you mention make it seem not worth it though.
CarPlay does not use Bluetooth for audio. Wired CarPlay uses LPCM, Wireless CarPlay uses AAC-LC for media. The iPhone will for sure perform the necessary transcoding. They would otherwise break any CarPlay implementation.I fear that Apple changed something with the Bluetooth codecs so it does not work anymore.
CarPlay does not use Bluetooth for audio. Wired CarPlay uses LPCM, Wireless CarPlay uses AAC-LC for media. The iPhone will for sure perform the necessary transcoding. They would otherwise break any CarPlay implementation.