First of all, congrats on the new (to you) 986
Between my 2005 XKR and my 2004 986s, I've bought and tried 6 or 7 BT to FM devices. They are all plug and play as you requested but none of them come close to CD quality, especially if you are in a city with lots of FM stations. But, they will let you play your music today without modding your car. The one which performs the best in my context is the Nulaxy KM19:
I have the best results (practically no distortion, no signal clipping and acceptable background white noise) by using FM 107.7 or 107.9, setting my iPhone 7 equalizer to 'small speakers' and 90% volume on the iPhone. I can answer the phone and use the KM19 buttons for next and prior song selection. It also has USB for phone charging and a second USB port for playing MP3??? (Just a guess, I've never tried it).
The KM19 has a 3.5 analog stereo input jack which might alleviate the clipping with without using the iPhone GE but the whole point for me was to keep the stock radio and not have any extra cables. There is a newer model of this unit available now on Amazon.
You do have to unplug the KM19 after each ride because it does not have a power switch and the 986 receptacle is always hot.
YMMV because these things are really sensitive to the particular car and surroundings.
Also, it works for me because the music only serves as a compliment to my Borla exhaust
