Hi! If it's about the overall appearance, different game engines might use different render engines, or varying default parameters for the scene lighting. A different lighting setup and a post processing layer adds a good bit of additional variation on the "vibe" of the environment.
Some 3d assets might also have a slightly different geometry than it is shown in the showcase images, because this asset pack is still in development, and I'm coming back to the previous 3d models that I'm not completely happy with, and making some tweaks, or rework them all together. The showcase images on this page might be behind an update or two.