Doubt that extra weight could be really critical. Of course, you do your own research for own good. But just as an opinion, you carry a bucket, it's pretty heavy, but it spreads over a large area, plus if the floor can hold furniture which is much more concentrated force, then the spread out weight of a 5 gallon cement should not add that much. Normally structures take 6 times nominal load. I will be using this on the second floor as well, albeit will level as much of it with the planer and belt sander, that floor is wood.
Regarding the final result, will be laying clickable laminate planks on the vinyl substrate. Vinyl is water proof and very strong, got me sold.
BTW thinking of garage usage, the layer is not strong enough to be used bare, it is easily sanded and scratched. Not meant for usage as a final exposed surface.