Highest quality to file size ratio

[Ischemia24]

I didn't see anything about this in the guides or FAQ and googling also hasn't turned up the specific information I'm looking for, so I'm asking here: How can I use H.265 to achieve the highest quality to file size ratio?

A year or two ago I found this post by Ma in the main HEVC thread. Based on that I've been using these Handbrake settings.

1080p
MKV format, 1920x1080, no filters, 10-bit H.265, constant framerate same as source, very slow preset, no encoder tune, auto-profile, 2-pass, 1500 bitrate, Extra Options: rc-lookahead=120:bframes=12:ref=6:subme=7
If it is a dark video then: rc-lookahead=120:bframes=12:ref=6:subme=7:aq-mode=3

720p (only listing what's different here and for subsequent resolutions)
1280x720, 760 bitrate

480p
854x480, 360 bitrate

360p
640x360, 300 bitrate

These are a starting point, and I've had to adjust the bitrate or try CRF instead, depending on the source files. But I've noticed that others have outdone me when it comes to the quality to file size ratio. It seems there should be a better set of options to start with, or I'm missing something in terms of what settings I should know to try to tweak in different scenarios.

I've seen these types of threads before and contributed to them, and they usually have answers like "just find what's right for you", but I would like to at least hear what baseline settings others use and what are the prime candidates for settings to tweak for those that value quality to file size as I do.