Services attach to Composite or Task nodes and will execute at their defined frequency as long as their branch is being executed. These are often used to make checks and to update the Blackboard. These take the place of traditional Parallel nodes in other Behavior Tree systems.
The Default Focus creates a shortcut to accessing an Actor in your Blueprints and Code by setting the focus of the AI Controller. By setting the focus of the AI Controller to an Actor, you can directly access it from the AI Controller instead of accessing a Blackboard key.
The Run EQS Service node can be used to regularly execute an Environmental Query System (EQS) template at assigned intervals and can update a specified Blackboard Key.
You can create Services by clicking the New Service button from the toolbar that contains Blueprint logic and (or) parameters.
Currently working on updating your plugin to support 4.25 as it brings a lot of useful features that can improve the AI component of the plugin.
Just a final update, forums have resulted in feedback that general practice is to cast to AI controller and get the controlled pawn instead of using SelfActor. Will propagate that through affected decorators and tasks for 4.25 support.