Under the Unreal Unlimited plan, your access to Megascans is licensed for use in Unreal Engine as UE-Only Content -- that means that any output (renders, game, demo, video, etc.) should be produced in Unreal Engine only.
Additionally, if you hold a license to Twinmotion, you may also import Megascans assets as UE-Only Content into your Twinmotion projects for the purpose of visualizing content within Twinmotion and exporting images and videos as permitted under the Twinmotion EULA.
You may use other tools at various stages in your pipeline, as long as the final product is in Unreal Engine.
If you want to use Megascans in other tools also, choose one of Quixel’s subscription plans.