In this video I explain technical options for customizing your Live2D VTube Studio models yourself.

I also get into choosing a model that allows for maximum customization.

A few premade models are being sold excplicitly disallowing customization of the texture file. But even those still offer two levels of customization: built-in expression sliders (if provided by the artist as part of the model), and hue adjustment of the ArtMeshes in VTube Studio.