Thank you a thousand times! The smooth scrolling is indeed something worth calling 'an issue' or 'a problem', so terribly annoying. But I was able to fix it, thanks to you. Have a great day!
Ctrl+Tab in the current version of Opera cycles tabs with a tab preview. Ctrl+Shift+Tab cycles with a preview in reverse. 1 and 2 cycle tabs without a preview. Any of these may be changed inside the keyboard shortcuts area like I mentioned above.