A bit OT, more like an update on re-scale/compression’s methods I mentioned
Either 'cause I’m lazy or stupid (hopefully both) and contrary to what everybody and their dog say, I never sharpen images after downscale, instead I use algos that retain the perceived original sharpness adapted to a smaller size, that’s what I tell doctor Martin.
Anyway, after trying newest and shiniest {cough cough, fart, smile} google’s compression algo Guetzli, which is unbearably slow, changed my WF to use Imagemagick’s convert to batch dowscale images and Mozjpeg’s cjpeg to compress them. Results are tiny MGP motherfucka group of pixels that travel fast through the interweb’s veins 
PS
These (mozjpeg) are working well 4 me
cjpeg -quality 84 -dct float -dc-scan-opt 2 input > output