We're working on a video to show people how to test - Google Page Speed Insights is currently unreliable (sorry to say) & so is GT Metrix - the most reliable results we are getting from Pingdom by selecting the server closest to your audience

https://tools.pingdom.com/

Always skip the first test  and then take an average of 3 tests - that's a more clinical way of doing it & allows for the cache to build + also avoid peak traffic times when testing.

If you are testing speed under Cloudflare, you will get variable results as your site is delivered by Cloudflare nodes & not your server - so you must turn "developer mode off" to get a real result whilst testing.

Hope that explains it