Installed image caching / lazy loading plugin and setup. New page tests are not showing improvements. How long to take effect?

First I tested current performance on lighthouse and webpagetest.org

I installed wp-optimize, and compressed the images and ticked the boxes for lazy loading.

Then I closed all browser windows and opened an incognito window. Tried lighthouse and webpagetest, and practically zero difference.

I also checked the images from web page test.org, and saw that it's still pulling the 1,300kb background image, when the compressed version on my site is only like 300kb.

It also recommends i "defer loading images", but I already ticked the lazy loading boxes, so what the fuck?

I'm guessing those testing sites cache stuff and cause inaccurate results? I want to know how much of a benefit it was to use wp-optimize..

Any suggestions?