General-purpose settings to improve quality (beyond the basics)?

[shae]

Assume a baseline of: CRF 16, --tune film, --preset veryslow.

What are the next generic things worth trying? At the expense of encoding speed and/or bitrate.

CRF 15?

-deblock=-2:-2 or -3:-3?

Will "--tune grain" necessarily improve matters?
Despite the higher resultant bitrate, it seems to potentially also result in smaller I-frames (higher QPs). While P/B frames might be larger, I'm not sure if it's enough to compensate.

[Emulgator]

restrict qpmax, restrict ipratio, restrict pbratio, lower deadzones

[shae]

These would be your next low-hanging fruit, after lower CRF?
What do you think about lower deblock?

If deadzones are mutually exclusive with trellis, any potential to harm quality?
What about aq-mode 2 or 3?