It should be bridged for 5V Pro Micro. Without the solder bridge cheap Pro Micro spit out only 4.6V instead of 5V at both VCC and RAW pin in my test. This is due to forward voltage drop of protection ...

If you're switching bootloaders, such as flashing QMK DFU on a Pro Micro, you will need to change the fuses, in additional to flashing the bootloader hex file. This is because caterina (the Pro Micro ...