I don't know what a good Terminal program is. I use linux.
An Arduino Nano has a usb-serial chip and the ATmega328P microcontroller.
If you upload an empty sketch, then you can use the usb-serial chip on its own, in the same way as a usb-to-serial-ttl module.
If you need another Serial/UART port on the Arduino Nano, then often the SoftwareSerial library is used.
The Arduino Micro has a spare hardware Serial/UART port. That is easier if you want to connect a serial device to an Arduino board.
The "Serial" port is to the computer via the USB cable and "Serial1" is the spare Serial/UART port at pin 0 and 1.
The Micro has only one communication channel to the computer. It can connect to a Terminal program or to the Arduino IDE, but not both at the same time.