Image optimization

Trying to optimize my photos before uploading to my media files in wordpress.

Tried using free softwares such as tinypng, kraken.io and bulkresizephotos, the pics go from 402kb -> ~183kb.
The cropped version of the same photos goes from 206kb -> 83kb.

How can I compress them even more?
I want them even smaller than 83kb, and I dont want to crop ever single photo to square dimensions, so is my only choice to have them max compressed at ~183kb?

Please explain

 

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