Bluetooth Airplay Incompatibility

iPhone 13 fully up to date iOS 16.6

Since I bought a Denon CEOL hifi which connects over airplay rather than basic Bluetooth I've found long used stable bluetooth connections don't automatically connect - particularly important when my phone doesn't connect to my 2015 BMW (basic bluetooth as the car is 7 years old) or my wife's 2020 KIA which has full Carplay.

Moving between the 1Mii B06+ [part of Cisco?] Bluetooth Receiver/Audio Adapter and the Denon

RCD-N11DAB Hi-Fi CD Receiver is particularly troublesome, but it also drops the KIA connection which is extremely troublesome.

My current work around for connecting the 1Mii adapter is:

1. switch Bluetooth off and back on on the iphone - sometimes works
2. 'forget' the B06+ connection - sometimes works, but sometimes requires more than one attempt

Moving back to the Airplay/Denon works more reliably

1. but sometimes takes more than one attempt.
2. Sometimes simply selecting the Denon even starts the system up from standby
3. Other times I have to switch the Denon on manually, then it will always connect - no 'forgetting' required.

For completeness

• I also use Microsoft Phonelink with my notebook which is equally troublesome, but can be fixed by refreshing the link from my laptop.
• I use Apple Music and BBC sounds to select what I listen to.

What can be done to make this really great feature work as it was designed?