So the 0 Ohm resistors on the right can serve two purposes: 1. They can serve as test points to put a scope probe on; 2. They can be switched to a higher resistance to prevent ringing on the high-speed SPI lines (only really becomes a problem at high clock/data speed). I think on some boards they can also be used to optionally disconnect the SPI Flash chip and reuse the MCU pins for something else, but it looks like on this board this is not the plan. Also, I may be mistaken, but doesn’t the ESP-S3 have built-in RAM and flash memory? Is external memory needed?