Good morning and welcome.
Congratulations on your new purchase
The most recommend mmi box is still the Mr12volt. I have the original version, and I've fitted quite a few to other owners cars since.
Shameless plug - I offer this service to UK owners (and anyone that wants to travel, or pay for me to go there :rofl: )
But I've also done a video on how to install them...
https://youtu.be/bwR3WHSBVXw?si=pKUWenBXhPBsWCxx
For the ones that like to do it themselves.
As for the rear camera, I did make an old video on this that can still be used with the Mr12volt box, but I'm in the process of updating that with new techniques.
There are other mmi boxes available, but all the others connect via the AUX socket (as opposed to the MOST fibre optic network with the Mr12volt box) I'vemade videos on these as well, check out my channel, link in my signature below. Now I never had an issue with the original box type and had one in mine for quite some time before fitting the Mr12volt box. It then went into my sons E93. But it's all down to quality, and personally I can't fault the Mr12volt box
Now you can read opinions that some have had issues with them, and fair play if they have, but owners have had issues with the OE equipment also!