In CRF mode, me and subme affect quality?

[MasterYGM]

Sorry for this basic question... (and poor english too)

In CRF mode, me and subme affect quality? or just affect compression efficienty?

except some subjective parameters (psy-rd strength, deblock strength) is there any option affect image quality in crf mode?

and... more basic question...
why should assign higher quantizer for b frame then p frame? in same quantizer b frame will have smaller size. why give higher quantizer again? x quantizer in p frame vs x quantizer in b frame has different visual quality?

[Dark Shikari]

Changing settings in CRF mode will affect both bitrate and quality. Raising subme from 7 to 9, for example, might increase bitrate by 2% and improve quality by 5%.

CRF is not a magical "exactly consistent quality across all settings" button.

and... more basic question...
why should assign higher quantizer for b frame then p frame? in same quantizer b frame will have smaller size. why give higher quantizer again? x quantizer in p frame vs x quantizer in b frame has different visual quality?Biprediction provides very good prediction even without any residual coded. You can generally get away with (and it is RD-optimal to) have higher quants in B-frames.

In x264, MB-tree ratecontrol helps account for the fact that in a high-complexity scene, B-frames should have roughly the same quality as P-frames, while in low-complexity scenes they should have significantly higher quantizers.