In an earlier answer, you said by just moving tags to the top, you have observed an increase of over 0.5 seconds. I have a follow up question : what are the tools you use to perform audits, and measure improvements?
There are loads of great tools out there, but my go-to tools every time are Webpage Test[1] and Chrome’s dev tools[2]. There isn’t much you can’t do with those two, and they’re free!