how do you optimize heavy VFX scenes without losing quality?

working on a personal project, and the part that's killing my schedule isn't the final renders; it's everything before that. the back and forth on lighting direction, material tweaks, checking how things interact. every test on a heavy scene costs real time

feels like there should be a smarter way to separate the iteration phase from the actual rendering phase. like doing the messy exploratory work somewhere fast and only committing to the full pipeline once the decisions are locked. but i've never fully figured out how to make that split work cleanly in practice, especially on scenes with complex light bounce or tricky materials where a fast preview might not be telling the whole truth

the specific thing i'm struggling with is trusting the preview enough to commit. i feel like if the fast version doesn't accurately reflect what the final renderer will produce, you're just adding a step rather than saving time

I want to know how do you guys handle the look dev phase specifically? Is there a tool or a specific workflow that gives you genuinely fast feedback without lying to you about the final result??