F401 Nucleo Espruino Question

And I thought software was complicated, sigh...

My F401 Nucleo has a sticker on the back that says "MB1136 C-01" and has only the X1 (8MHz) crystal.
My F411 Nucleo says "C-02 and has X1 & X2 Crystals.
I understand that the X1 crystal actually belongs to the ST-Link portion of the board but could theoretically be used by the STM32F4x1 if configured properly.

What does "MCO" stand for?
@asez73, your F401 appears to run at 84MHz in your testing, yes?

Not oddly, I am still somewhat confused. Are these the 2 possibilities?

1. C-01 board, no external crystals used, no external crystals present except for X1 (8MHz) on ST-Link board, uses internal clock, runs out of the box at 16MHz, can be configured for 84MHz, but not as accurate as if it had/used an external crystal, and actual speed can also vary with temperature.
   
2. C-02 board, has X1 and X2, uses X2 (32.768KHz), runs at 84MHz out of the box, very accurate within the (fairly broad) temperature range.
   
   

I suppose adding X3 (and caps etc.) would allow you to break off the ST-Link if desired and still use an external (8MHz) crystal.

If I added X2 and the caps and moved around the resistors, my F401 Nucleo would boot up at 84MHz using external X2 crystal, yes? No software initialization needed.