Win10 actually is slimmer than Win7, as well I don’t think current versions of Unreal even function in 7, but I haven’t tried to use 7 since I upgraded an army of 2GB all-in-one PCs to 10.
I have doubts that it’s even possible to package anything other than an empty room in Unreal in 4gb, but virtual memory will do wonders, even if it’s slow af.
8gb is probably barely cutting it. I just upgraded to 96GB, and I might bump it again soon because I’m still getting some OOMs when packaging