This is going to be vague so I don't know if it is actually helpful... I have not experimented with bluetooth and axoloti, but I have tried out a couple of bluetooth modules with a Teensy. My experience was that it was very easy to figure out how to set up the module, but the hard part was figuring out how to interface with existing BT devices that I wanted to use as controllers communicating with my teensy. So it depends a lot on what it is you are trying to do on the other end... what other device you want to use to communicate with your axoloti (assuming it is just as easy to get the module to work with axoloti as it was with teensy). If you are building your own controller device and can pair up a second HM-10-type module as the 'other end', you are likely to have lots of easy success. If you are trying to use commercial BT devices, it is much more variable because bluetooth is quite complex. There are many different bluetooth "profiles" specifying different communication protocols, and the HM-10 is not going to end up being compatible with all of them. So an important first step is to understand the bluetooth setup on any device you are hoping to communicate with.
Again, that's not super helpful, but maybe it's a small start.