Hi there !
One question : when i'm recording my amp with the Captor x connected to my interface (no real cab, only with monitoring speakers connected), the signal is significantly louder than the signal heard during playing. Is it normal?
Is it when you playback the track you have recorded that it is louder than when you were recording the take? If so, check your settings in your DAW, and the levels in the project. If you are listening to the input of your interface when you are recording (direct monitoring) you are not going through your DAW to listen to the amp. This could be why the playback is higher if your track has plugins to boost the signal, or the fader level is higher than 0dB,etc.