The Vroid system is linked to several games and programs, most are listed on it's web site
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, plus they allow you to make NSFW models (you just have to find and download better textures), also two things in these forums also can use .vrm models
Anime Assistant and
Desktop Kanojo, so you have options for testing things out. As for things that use Vroid character images in games, I haven't found anything there.
Koikatsu does have a more extensive character creator and if you get the Better Repack versions, it comes with a studio mode to make scenes and images with. Again I don't know of any games that use images made from this, besides itself.
Since Vroid Studio is free, it doesn't hurt to try it out and its a smaller file size and less resource intensive compared to Koikatsu.