This is an old question - but the order of input delegate events vs actor ticking has been bugging me for a couple of days now and I think I found the answer by simply attaching the debugger to a compiled version of the engine (4.22 in this case), and checking the callstack when a bound input delegate is called:
APlayerController has a tickgroup of TG_PrePhysics:
(more on tick groups)
During the APlayerController tick, ProcessPlayerInput is called, which fires off all the bound delegates for registered InputComponents
So, bound input delegates are called during TG_PrePhysics - here’s the callstack:
UE4Editor-DASH.dll!ADASHPlayerActor::OnBeginDash() Line 123 C++
[Inline Frame] UE4Editor-Engine.dll!TBaseDelegate<TTypeWrapper<void> >::Execute() Line 561 C++
UE4Editor-Engine.dll!FInputActionUnifiedDelegate::Execute(const FKey Key) Line 252 C++
UE4Editor-Engine.dll!UPlayerInput::ProcessInputStack(const TArray<UInputComponent *,FDefaultAllocator> & InputComponentStack, const float DeltaTime, const bool bGamePaused) Line 1306 C++
> UE4Editor-Engine.dll!APlayerController::ProcessPlayerInput(const float DeltaTime, const bool bGamePaused) Line 2473 C++
UE4Editor-Engine.dll!APlayerController::TickPlayerInput(const float DeltaSeconds, const bool bGamePaused) Line 4461 C++
UE4Editor-Engine.dll!APlayerController::PlayerTick(float DeltaTime) Line 2134 C++
UE4Editor-Engine.dll!APlayerController::TickActor(float DeltaSeconds, ELevelTick TickType, FActorTickFunction & ThisTickFunction) Line 4601 C++
UE4Editor-Engine.dll!FActorTickFunction::ExecuteTick(float DeltaTime, ELevelTick TickType, ENamedThreads::Type CurrentThread, const TRefCountPtr<FGraphEvent> & MyCompletionGraphEvent) Line 164 C++
[Inline Frame] UE4Editor-Engine.dll!FTickFunctionTask::DoTask(ENamedThreads::Type) Line 285 C++