Scene Optimizer:
https://f95zone.to/threads/scene-optimizer-mar-2019.9973/ - download link here, but it's well worth the money if you can afford to drop money on DAZ stuff.
Keep in mind, the denoiser can help get rid of noise, but it kills detail (especially stuff like small details on skin). I've found good results with Intel's Open Image Denoiser, since it's not as overzealous as Nvidia's one that's built into DAZ. But I don't remember where I found the download link for an executable/installer. Sorry
As far as scene lights are concerned... there are three main ways to put light into a scene:
There are really no limits I'm aware of on
how many lights can be in the scene (Iray rendering is very different than the way game engines work, in which you do need to limit the number of lights. Usually.) Indeed, if you're using mesh lights, how do you even say "how many" lights you're using? You might have 3 meshes, each with 2 or 3 emissive surfaces, which are spread over 100 or 100,000 polygons. So, "
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" is the wrong way to think about optimization in DAZ.
Rather, what makes your scene render quickly is the physical amount of
light surface that exists in the scene. A scene that's lit by several large emissive meshes will render much faster than the same scene lit by a tiny, super-bright light bulb filament. Of course, there's a tradeoff here: large light sources will make the scene lighting look "flatter" and less intense.
There are also more complicated things about scene geometry/materials/shaders that make the scene slower or faster to render, and I haven't begun to understand all of it. The best thing to do might just be to try out different environments until you find one you like the look of, which also renders quickly enough for you.
That's the frustrating thing about rendering - everything is a tradeoff, and there's no magic solution to give you an amazing image quickly (except maybe buying 8 RTX 3090s lol)
Good luck!