Yes. that’ s correct.
Regarding your second question, what I can recommend you is do not use use X to start with, see where use GenServer will go, and if it makes sense where you will have to define the callbacks. Then try to abstract things into X.__using__/1 and see what will make the best use of use X. remember use just inserts code. You can pretty much copy and paste and port the quoted parts. You will figure it out.
