Choose a representative video with motion, dark scenes, dialogue, and subtitles. Encode it in HandBrake at two or three settings, then compare the results on the actual playback devices. Inspect visual artifacts, audio sync, subtitle behavior, file size, and processing time.
Presets are a starting point, not a guarantee. Keep the untouched source until the delivered file has been watched and verified. If the conversion will be repeated, save the preset and tool version so another operator can reproduce the result.
Akousa