Hi,
1) Hereby, I have attached the .mex file and screenshots of pin & clock configurations in the MUCXpresso config tool for your reference.
PIN configurations:

LPC54018 - Package selected as 208PIN:

System Clock configured as 96MHz:

Flexcomm 9 (SPI) peripheral clock configured as 96MHz:

2) About your two projects, the only difference is XIP and no-XIP? Yes.
In No-XIP, we configured system clock as 180MHz.
In XIP, whatever the system clock we're getting SPI clock and data but there is no trace for the communication with the TFT ST7789v driver.
3) I mean the "Digital Oscilloscope"
4) Hereby, I have attached the ZIP file - XIP project developed from helloworld_XIP SDK example project for your reference.