もう少し調べてみたら>>137に補足すべき点があったので追記。
RCAをNGU Sharpと一緒に使う時の挙動
・RCAのqualityがmediumの場合 →NGU Sharpのlumaがhighにされる。
・RCAのqualityがhighの場合 →NGU Sharpのlumaがvery highにされる。
参考１：下記URLの「run as part of NGU, if possible」のとこの説明 (※0.92.10対応の記述のアーカイブ)
https://web.archive.org/web/20180206120240/https://forum.doom9.org/showthread.php?t=171787
> Combines most of the work required for 'reduce compression artifacts' into NGU Sharp upscaling
> for a large performance advantage when both are run at the same time.
> With this option enabled medium quality forces NGU Sharp to high
> and high quality forces NGU Sharp to very high.
参考２
https://forum.doom9.org/showthread.php?p=1833027#post1833027
> FWIW, "reduce compression artifacts" currently only works for free
> if you use NGU Sharp in High or Very High quality, but I plan to make it work for Medium, too.
訳：
RCAがコスト無しで動くのはNGU SharpをHighまたはVeryHighで使った場合のみ。
いずれMediumでもそうする予定。
