Everything in the toolkit is made with blueprints and you have access to everything I have access to. The AI is done through the abilities (as well as the Ability System to a lesser extent for units who implement this component ).
Most of the important AI code is in BP_Ability, with specific abilities overwriting and adding to the code of this parent blueprint.
To check out how it works I recommend adding a break point on the selection of an AI unit and then stepping through the nodes one at a time to see the entire system in action.
The AI works in a similar fashion for all of the included abilities. First the ability finds all potential targets of the ability and assigns a value based on some criteria (health of the target, for instance). Then it assigns a value to all tiles that can be moved to from which the ability can be used.
It finds the highest product of these two values and compares it to the equivalent product values of any other abilities the unit has (if it implements the ability system). The highest value determines the ability to use, the tile to move to and the target to use the ability on.
The devil is in the details, of course, and AI is one of the more complex parts of the toolkit. Let me know if you need any more help in figuring things out after stepping through the code.