If I understand well you ask if the COM port of USB will be the same than bluetooth COM port?
Of course no, the .ino (so program in the nano) don’t deal with COM port, just windows do it, Bluetooth device when paired create two COM port (input and output but I’m not sure of the translation), it’s output port which must be used.
Example :
- USB on COM3
- BT input COM4 (unused)
- BT output COM5
You select it via AGIO.