I’ve used these setting for re-encoding and the quality is very good. Even DVDs look better in many cases. Haven’t done any B&W though. Be warned h.265 encoding is very cpu intensive e.g. with my Ryzen 7 7700x re-encoding a bluray movie takes about 90-120 mins at 1080p. Down scaling will reduce that time.

File size doesn’t equal quality e.g. h265 encoded titles usually take less space than h264 encoded titles and the quality is imho better. For example from my own collection (ripped from my own discs) Dune 2021 Part 1 1080p 5.2 GB h265 re-encoded + original soundtrack + subtitles.

The 20+ GB files are typically not re-encoded bluray (AVC/VC-1) or 4k releases.

For a proper 1080p release with bluray audio expect anything from ~5GB up.