The tabs are rendered in a completely illegible manner, with transparency and overlap, and without any cropping of favicons.
It completely ruined any remaining accessibility - please compare current version from Opera One vs. Opera GX. I admit I have a lot of tabs open, but they were distinguishable from each other previously, while right now it's a mess.
Why don't you test your soft on edge cases, instead you choose to go the safe path with only 3 tabs opened, with a full-screen window, and claim success afterwards?
Hope this cancer from O.O doesn't reach O.GX. If so, I honestly admit I will have to switch to Edge.