The GPIO output drivers are connected to the following
The output drivers of I/O Ports P0 and P7 are connected to VDDD. Output drivers of I/O Ports 1, 2, and 5 are connected to VDDA. Output drivers of I/O Ports 3, 4, and 6 are connected to VDDIO.
Reference. Pg 11 of PSoC 4200 M datasheet.
Depending on what ports you have chosen for LIN, the output levels depends on the respective power supply mentioned above.
Refer to the schematic of CY8CKIT-026 CAN and LIN Shield Kit for reference:
Also refer to the Section 6.5 LINE DRIVER/RECEIVERELECTRICAL -> DC PARAMETERS in LIN specification as well.
3.3 V or 5 V can be chosen based on the transceiver specification. Also, 3.3 v leads to lower power consumption compared to 5 V but the noise performance will be better for 5 V level.
Thanks for explanation, everything is clear now.
Stay safe and healthy!