Why there is no single “right” format
Marketplaces usually show videos in 1:1, social apps in 9:16, your own landing pages in 16:9. Render only one variant and you give away either visibility (letterboxing on social) or conversion (cropping on marketplaces).
Recommendation per use case
Buust renders all three variants per product in parallel — you pick the right one per channel. Your render budget doesn’t go up, because the same source is just computed three times with a different composition.