There are nine pins on the ESP32-WROVER-E that are marked NC (no connection). Does this mean that there is no internal connection to the pin, so it can be grounded or have tracks routed through it, or does it mean that connecting to this pin is not permitted?

I have an EPS32 app that uses uart_write_bytes and uart_read_bytes. I want to port this to an ESP32-C3. Can I use the JTAG serial port with uart_read/write_bytes? If so, which UART_NUM do I use? If not, is there another way of writing/reading to the JTAG serial port?