Improve works one shot at a time on its weakest dimension. The global optimizer (Review tab) looks across the film.
It reads every scored render — visual, character consistency, prompt adherence, cinematic, continuity, audio — finds the dimension with the lowest average, and lists the regenerations that would lift it most per credit spent. Give it a budget and it stops at the budget.
The plan shows the current and projected average. Tick the regenerations you want and Queue — each is an ordinary Improve generation with its usual cost. Untick anything; the optimizer never spends on its own.
It needs scored renders to work from. A project whose renders have not been scored yet gets an honest "nothing scored" rather than a made-up plan.