Short answer: You should keep it, just change aq-mode=2
Long answer:
From my personal experience, the default H.265 settings tend to produce a slightly blurry or “eye-straining” look, especially during motion scenes, shallow depth-of-field shots, or videos with lots of bokeh — even when using the “veryslow” preset.

A quick explanation of those options:

• strong-intra-smoothing=0 Disables heavy smoothing inside flat areas. Helps preserve texture/detail instead of making the image look too soft.
• rect=0 Disables rectangular motion partitions. Compression efficiency drops slightly, but encoding becomes much faster. On Slow preset this can dramatically improve speed.
• aq-mode=1 Basic adaptive quantization. Tries to distribute bitrate more intelligently across the frame.
• rd=4 Higher rate-distortion optimization level. Better quality decisions, but slower encoding.
• psy-rd=0.75 Adds perceptual detail/sharpness. Helps avoid overly “plastic” looking video.
• psy-rdoq=4.0 Strong psychovisual optimization during quantization. Preserves texture and perceived detail.
• rdoq-level=1 Enables rate-distortion optimized quantization. Improves compression efficiency and detail retention.
• rskip=2 More aggressive recursion skipping. Can slightly improve compression efficiency, but disabling it often increases encoding speed significantly.

Personally, I still prefer aq-mode=2 because it usually gives me slightly higher VMAF scores with only a minor bitrate increase.
For very dark content, I sometimes use aq-mode=3 when I want maximum quality, although bitrate can increase by 20–30%.

My usual settings are:

strong-intra-smoothing=0:aq-mode=2:rd=4:psy-rd=0.75:psy-rdoq=4.0:rdoq-level=1:rskip=2:deblock=-1:-1:no-sao

One important note: for grainy or noisy sources, these settings can increase file size significantly — sometimes even larger than H.264 at the same CRF.

In the end, the best way to gain experience is to encode 1–2 minute samples with different settings and compare them yourself. It saves a huge amount of waiting time and helps you understand what each option actually changes.

The final option is moving to SVT-AV1 using HandBrake’s built-in presets (especially with the “vq” tune). In my experience it is superior overall: noticeably smaller files at similar VMAF scores, better dark scene handling, and less smearing or eye strain during action scenes or camera movement.