Render preview
The editor's canvas is a faithful live approximation; for a pixel-exact check of one variant, use the render preview — it runs the real pipeline for a single variant at reduced resolution, so you can inspect the actual output before rendering every variant. Settings → Render settings → Preview quality trades file size against sharpness; it never makes the preview unusable.
The preview takes the same per-stack lock as a full render: while another process renders that stack, it is refused with the message naming who is rendering. Wait for that render, or cancel it there.
The preview runs the whole pipeline — silence cut, hook, endcard, voiceover, motion titles, captions, loudness and the outro clip — only at a smaller size. The one thing it leaves out is the randomizer, whose tweaks are random per file and have no single "true" result to preview.