Renpy automatically, iirc, down scales images if they are larger than your current resolution. So it gives zero benefit to render, and distribute, in 4k. The only reason you would render in 4k, or more, is to use super sampling as Daz does not have a built in AA function (I think anyway. I render all my stuff in blender, only use Daz to build the assets - Don't need to super sample in Blender). Downscaling an image helps with unwanted noise in an image. Noise that s pretty much non existent in Blender these days to the awesome denoiser it uses in Cycles.
Anyway, the point is... Stop rendering everything in 4k. Most people utilise monitors of a lower resolution.