It has been awesome until 2013 when they decided to make their browser a skin on top of Chromium. Now they had more UI revamps and it doesn’t work or feel like Opera at all. I tried using it sometimes ago and now they even got those weird huge buttons…
Don’t get scared. Even when you f*ck up the most you can just wipe out the theme related files from your home folder and start from scratch. GNOME is probably the least customizable, among DEs KDE, XFCE, LXDE, MATE, they all work well, or you could also try tiling wms or classic wms like fvwm…