They have tons of cases, including those with minimal RGB, but yes, those are gaming PCs.

It is not exactly what you asked, but if it is customization and expand ability you are looking for, did you consider custom build cites like cyberpowerpc.com? You can select from wide variety of components, they build and test it for you, and make sure that everything is compatible and working. You do pay a bit premium for the assembly and tests but it is not that much, and you save your time and have a peace of mind that everything works.

According to global trends, your twin did not succeed either. Sorry.