Arduino - > x86 integration / interoperability?

I'm putting together a portable with an LTE connectivity. I'd like to have the Arduino on most of the time and only wake/boot the x86 system when required. Regarding this, I'd like to confirm:

- The m.2 interface for an LTE modem is only accessible from the x86 side, not the Arduino side

- The Arduino is totally separate and not integrated to the x86 computer through the motherboard, so I'd have to get an Arduino compatible LTE modem and wire it up through the headers. 

Do I have this right?