Hi,
I will just write down what we have answered to your ticket, so other customers can see it. Everyone that has any thoughts on this can share his experience!
Here is our answer:
We have encountered the same problems as you, but unfortunately some things in nopCommerce are not perfect.
For example, the image minification is really bad. I have tried uploading a highly optimized image with size ~40KB and after it was saved in the database by nopCommerce it became 120KB (then Google suggests me to optimize the images of course).
About the render blocking CSS and JS there is a huge discussion in the nopCommerce forum. It is the same for the HTML minification.
About the resources you are fetching from Facebook, I do not think there is something we can do.
I do not know if you are using it, but I suggest you Pingdom.
I hope this information helped !