If I am correct, the first two pins (RX/TX) are connected to the USB, and I cannot use the serial monitor and the first RX/TX serial ports at the same time.
But, what about the other 3 auxiliary serial ports? Are they separated? Do each one of them has it's own buffer?
For example: Is it possible to add, let's say, four Bluetooth modules(Let's say HC-05) and use each of them for a different purpose?