Finally got the SD Card working! Turns out the CS Pin is connected to GPIO1, not GPIO2, due to a pin mix-up in the library. Simple software fix, and it's like magic!
Also, I would recommend verifying that you don't have a corrupted Chinese-knockoff SD Card, as this will also cause you headaches and make things more difficult to solve.
For the SD test, we actually used the Arduino SD_Test Example, which worked out of the box (with our custom board library):
Had to find the MAC Addresses of the devices first, so I used this program:
Issues with I2C:
Had some issues with Serial Monitor not working, and the device not being recognized, it was confusing to get down, but I solved those issues.
ERR light turns on during operation
Apparently this is normal, ERR LED is connected to GPIO21, which is the Debug pin on the ESP32-S3. This means that it pulls low when it's in debug, and defaults high in regular mode (although this can be overridden in code [TESTED]).