To not bury the lead: keyboard control works no differently for FM-X vs. AWM2. You can ignore this distinction (which engine, FM-X or AWM2 is used). Keyboard Control works the same for both.

When "Kbd Ctrl Lock" is turned off:

1) Each PART 1-8 can be individually selected (on or off) for keyboard control.
2) PARTs 9-16 cannot ever have keyboard control for the PART turned on
3) Keyboard Control ON is indicated in the [PERFORMANCE] (HOME) screen by a greenish picture of a piano keyboard. When Keyboard Control is OFF - the same picture is grey.
4) Keyboard Control is a feature of the PART - and does not depend on the engine the PART is using. Keyboard Control works the same for FM-X, AWM2 (drum or normal PARTs)
5) Keyboard Control PARTs are only layered (only play at the same time when you press piano keys) under two conditions:
a) if NO PARTs are selected. This can be accomplished by pressing the [PERFORMANCE] (HOME) button. Another way of saying "NO PARTs selected" is to say that "COMMON" is selected. Having no single PART selected means that the Performance Common level is selected. Montage has two [COMMON] buttons located to the right of the touchscreen and the upper [COMMON] button is also a way to deselect all PARTs (thus selecting "common" ).
b) if any one of the PARTs with Keyboard Control ON are selected. Note that selected PARTs have a white outline around the PART inthe [PERFORMANCE] (HOME) screen. And you may need to check PARTs 9-16 to see that no PART in that range is selected. Or look at your PART SELECT buttons after pressing the [PART CONTROL] button.

So in order to use FM-X and AWM2 keyboard control - just ensure the following:

1) Both PARTs (or groups of PARTs) are located in PART slots 1-8.
2) Make sure "Kbd Ctrl Lock" is turned OFF
3) Press [PERFORMANCE] (HOME) and touch the keyboard control icon for each of the PARTs (AWM2 and FM-X) you want to play together if that icon is not green (if the icon is grey).
4) Either press [PEFORMANCE] (HOME) to deselect all PARTs (to select "common" ) OR ensure that one of the PARTs 1-8 with keyboard control ON is selected.

What if you have the "wrong" PART selected?

If you have a PART selected that has Keyboard Control turned OFF - which means ANY single PART 9-16 (ever) or any single PART 1-8 that has keyboard control=OFF, then what will happen is that the PARTs with keyboard control=ON will not be triggered. Only the single selected PART (the single PART that has keyboard control=OFF) will be triggered. The way I think about it is that if I SELECT a PART with keyboard control=OFF, I "pretend" that what's happening is that the keyboard control=OFF PART I have SELECTED turns its keyboard control=ON (even if it's a PART 9-16) and turns keyboard control=OFF for ALL other PARTs.

This is why it's important to keep track of which PART is selected when dealing with how Keyboard Control is working.