I know this question is some kind of weirdo but I want to know 
What is noise reduction option in coreelec settings, it is equally useful for FHD, UHD (Heavy bitrate) source or it is only use for kind of sd or old dvdrip type source (movies). I want to know that what is difference with enable noise reduction and disable noise reduction (about picture quality).
Thanks in advance.
Why don't you check it yourself? If you can't see the difference, then doesn't matter...
It is mostly there to fix playback of some live channels. If you don't see any problems with Live TV playback, you probably don't need to use those options.
They were made available in the UI so that users wouldn't have to use command line commands to tweak these advanced options.
Disabling noise reduction is very useful for S905W and S912 boxes, no need to disable on S905 and S905X.
