ESP32S3 : VDD_SPI Voltage Control

[ThomasESP32]

Good afternoon,

I have read the Esp32S3 reference manual part VDD8SPI Voltage control.
Could you please explain me the difference between a configuration where the VDD_SPI is powered via 1,8V LDO Internal regulator
and a configuration where VDD_SPI is powered via VDD3P3_RTC pin ?

Which SPI is concerned with this configuration ? Is it the SPI that is connected to the Flash Memory embedded in the module ?
And what happen if the configuration is 1,8V LDO ? Does this mean that the SPI pins voltage will change between [0; 1,8V] only instead
of [0; 3V3] ??

Do you have any explanation concerning this point please ?
Best regards,

Thomas TRUILHE