Hi there,
Of course ! The whole point is to eliminate variables so that the comparison starts on solid ground. These screenshots establish that it is possible to recreate the render quality of the online editor in regular UE, so that takes care of the quality question. Now it’s your turn to drop either of these two characters (Ettore, Bernice) in that interior scene of yours. Once that is confirmed to look consistent with the online editor to you, and your scene is reworked to display them at a quality that you find acceptable, then it will be time for you to look a the potential issue (if any) with the customized heads. I currently do not have the time to play with the online editor or wait for a custom asset generation and download. Unless you provide the downloaded zip with all the uassets of course.
And then there’s also the comparison you can do with ortho/telephoto renders.
For a grey BG I either assign a material to a plane or a sphere, or use a fog asset. The screenshots were taken in 4.26.