Mostly I start with some previously made pose and modify it.How do you pose the characters?
Default dialsDo you use the default dials in Daz? Or ActivePose? Or the Translate tool? They all feel very counterintuitive for me.
Cheat - hide non visible in scene elements ordelete them. Or create render of the background and put it as plain with this image set as a background.About your animations, 120 pictures in 6 hours. That's 3 minutes per render. Wouldn't that be insufficient to produce quality renders? If I only use 3 minutes for my renders, they would be extremely noisy, and while a denoiser would help, it would look very smeared. But your renders don't seem to have such a problem.
Everytime when I create scene with more than 3 characters (Genesis 8)Your scenes are also quite big. How often do you get to fit them in your VRAM after optimisation to be rendered by the GPU?
I just rener image several times and switch off and on some elements for those renders. And I merge them in PS