Well, the download page for GX gives an overview of the general features. GX has all of the primary features of the standard version but with a load of great new features that may or may not be released in the standard version.
That said, if you're asking about what data will be synced if you make the switch from standard Opera to GX... as far as I know, all data that you have set to sync will auto-sync to GX (except speed dial, I believe) as long as you're signed in to your Opera account on both. Don't quote me on that but I run GX on my PC and standard Opera on my laptop; all that I have set to sync works on both of them without any noticeable lag.