to habe the mini not offsetting incoming CVs, you have two solutions:
At startup, if you don't use the keybed, (receive midi), the default transpose is 0. But as soon as you hit a key, you won't be able to go back to 0.
Using an external midi/usb source, if you send midi note 12, it will set it to 0 too.
The octave -3 option you have on the micro will be implemented on the Mini for the next firmware update.