It's not a stupid question, don't worry about it. And what i'm about to explain applies to the Switch specifically, PS4/Xbox One/ PC don't have to deal with this. Unreal Engine is good, it's just you kinda have to optimize right when it comes to the Switch. PS4 and Xbox One don't have to deal with it and if your PC is good enough, you can run some of the higher end Unreal Engine games.
Because it's also a handheld, the Switch isn't as powerful as the PS4 or Xbox One and as a result, sometimes ports of 3rd party games get the short end of the stick. For example, the Switch version of Ritual of the Night runs at 30 FPS, 720p and on handheld mode, it runs even worse. The other versions of the game run at 60 FPS, 1080p. That's an example of a game using Unreal Engine though, sometimes games that don't have that still don't run as good on Switch as they do on other platforms, though by how much varies. Atelier Lulua on Switch runs worse than it's PS4 counterpart but it's such a minimal difference that it's unnoticeable. The worst case scenario is that sometimes a game just can't run on the Switch. There's a reason why the Switch only gets Final Fantasy 15 Pocket while everyone else gets the real version of the game.
It's worth noting that this only applies to 3rd party games that have different versions. 1st party games and 3rd party games exclusively developed for the Switch (that may or may not have gotten ports to other platforms such as Octopath Traveler) don't really have this problem.
There hasn't been a case of a Switch port just being so inferior that it's unplayable but i would prefer a game to run better. Like i'm still having fun with Ritual of the Night but i'm definitely playing the worst version.
At the end of the day, the graphics don't matter to me as much but i would prefer a better performance. So when Atelier Ryza drops on Switch in October, i'll still get it even if it ends up as the noticeably worst version. I'd just prefer it if it wasn't that. Now, i'm going to admit, i'm actually not 100% sure if Atelier Ryza is running on Unreal Engine. I think it is because of how it looks but i could be wrong and they're simply just using a new visual style. And i'm actually not sure if my post here is 100% accurate but at the very least, this is the gist of the Switch's occasional issues with 3rd party games.