[HELP] how to get the super best encode quality? no consider hard disk space

[ssdde]

If you want lossless quality and smallest file size then using preset placebo is fine (personally I would stop at 'very slow').
In general 'slow' and 'very slow' are the presets which are fine for me and if it's a simple reencode I usually will go for crf 16, but post folks are fine with 18-22.

Cu Selur

so if i always choose using CRF 15, preset: placebo, is it always a good choice? though the encoded file a little big.

how about AVC profile/level setting? always High, and over 4.2 or unrestricted?