Looking for suggestions, tips, opinions. Using poser 2014 game dev version.

I'm making a promo animation for a childrens' book.

Has to use Firefly render. (tried octane, and it looks fast, but demo doesn't allow animation so I can't really test it in there)

It will be for a YouTube video at 480p: 854x480. I would prefer 1080p: 1920x1080, but I'd be dead of old age before it finished.

It's approximately 30 seconds. Scene has a forest, car, 3 people, rocks grass and more. In a word, BIG.

Render settings have always baffled me.

Cast shadows has to be on. Raytracing too.

Unclear about Subsurface scattering or irradiance caching, or indirect light.

Pixel samples? how low can I go?

I will be rendering to images.

Any suggestions for the LOWEST settings I can get away with and still have it look okay? It doesn't have to be Pixar quality.

Thank you.