But what is the best and what developers want? There are many tutorials to get good score..
To expand your understanding a bit, it is not enough to just optimize a website to get a high score at PageSpeed & Co. As I have already tried to explain to you, neither PageSpeed nor GTmetrix measures the actual loading time, but rather focus on the display time and the time for the actual loading of the sources is almost completely ignored. If it takes 10 seconds or more for all sources to load, then that doesn’t help you or your visitors very much if the display time is only 1 second. It ended up being 11 seconds, but most of the test sites don’t take that into account.
When it comes to optimization, it’s about 2 things. On the one hand, to load all sources quickly, especially the main document, and to optimize the loading behavior of static sources such as CSS, JS, images, etc. You therefore need a page cache and optimization of the static sources to ultimately reduce the loading time AND the improve display time.
With the LScache plugin you get both and on a level that no other optimization plugin can. And of course you can undo all settings!