Start with intent: chat shares tolerate lower bitrate; archives or big screens need more quality. Smaller targets mean stronger compression and more visible artifacts. Dropping resolution (e.g. 4K → 1080p) often beats bitrate alone. H.264 is widely compatible; H.265 saves more bytes at similar quality but may encode slower. Use MBox’s target size slider for quick goals, or Advanced mode to tune CRF and output format — balance size and clarity for your workflow.