OK, bejant was quicker onthe keyboard than I.
Looks like we both said the same thing. I will add this. - If your taking the clones out of the original document it would be easier to just use simple copy and not have the original parts brought in if your looking to improve performance, if you don't copy along the original part, the clone basically becomes a simple part anyway, after a warning message or two.
Clones are parametrically linked to their origin, simple copy are dumb objects and have no linkage. Simple copy is probably better unless you expect to / or want to make changes within the assembly. Personally, I export .step versions because I may use them in the future with the Assembly branch. But that's just my personal preference.
A manually assembled model with .step parts.