Cloners, instances and other C4D specific things cannot be exported to UE4 and need to be converted to polygon objects.
However, you can also just export the original object and do the cloning in UE4.
That way your scene can still benefit from various rendering optimisations the engine offers.
It always depends on the circumstances.
Noone would want to export a whole forrest as a single mesh, but you’d also wouldn’t want to split the
handles of a cupboard into their own mesh just because there’s more then one copy of it.