If you're logged in to Sync already, there's a section of Settings on what data to sync. A direct URL (which you'll need to copy and paste into tje address bar as links to Settings are not clickable in the forum)...
opera://settings/syncSetup
I don't know how to access a similar setup in Opera for Android, and likely not all data in Sync is available there - but obviously any data not enabled in Sync won't be.