To be clear...Both options give you a Bluetooth "INPUT" into the Goldwings existing audio system and speakers using the AUX 3.5 audio connector in the glovebox.
The "Block Diagram" description is...A Bluetooth enabled phone will send an audio stream to the Bluetooth enabled receiver in both options A & B. The Bluetooth receiver then sends the audio through the connected AUX 3.5 audio connector to the Goldwing audio system to be played through the speakers or connected headset.
I'm gonna say option a will be the same or lower in volume than just plugging your phone in on the 3.5 AUX plug. The Electrical Connection Bluetooth Receiver shouldn't amplify, just create a wireless Bluetooth connection on the AUX 3.5 audio input.
The Neoteck will amplify the audio signal coming out of the Bluetooth receiver, BEFORE the audio is sent to the AUX 3.5 audio connector, then on the Goldwing audio system.
You could just COMBINE both A & B options into one and test it in steps. The USB Bluetooth adapter in option B "COULD" be replaced by the Electrical Connection Bluetooth Receiver, which allows you to easily move it BELOW the left side pocket and opens up a USB power connector. Get the Electrical Connection Bluetooth Receiver to start with and see how loud it is. Then purchase the Neoteck AMP if you need more volume. My electronic experience tells me the AMP may overdrive the aux 3.5 input and be more of a problem in the long run. I Do recommend leaving the AMP accessible in the left pocket so you can adjust the Volume knob if your phones MP3 streaming is louder than Internet radio streaming.
You will be able to change to FM1, FM2, AM, and USB just like always.