It depends on your implementation and what you are trying to achieve.
Just to add forces in a specific situation (like colliding with a pawn), you should be able to apply the force you want to the component/body you want using the normal API in the game thread.
The async physics system will take care of applying it at the correct time in the physics thread.
The Async Physics tick allows you to do specific work each time the physics engine advances one step (which is not necessarily each time your actor/component ticks, because with async physics the physics engine tick and the game thread tick are decoupled).