If the video looks "blocky" in dark scenes, increase your player's brightness/contrast or enable a "sharpen" filter. Some players (like MPV) have built-in debanding filters.
While they look fantastic on tablets and laptops, the "micro" nature of the bitrates can lead to slight crushing in dark scenes (macroblocking) when blown up on a 65-inch 4K TV. Final Verdict MicroMKV series micromkv series