Hi,
The PFE_UART_RX/TX signals are for NXP internal use only, they are not for general application use.
As for more UART ports, as you are saying, 7 UART ports is the limit for the S32G2. If you are looking to add more ports, there are available chips that could be connected externally to the S32G to add more serial ports. It just depends on the general implementation you are trying to achieve.
Please, let us know.