It shouldn't cause problems but traces of the jailbreak will still be there. If you want to make sure that there are no traces whatsoever, a full restore would be your only option.
If you're not concerned about having some files left over then using a backup shouldn't cause problems.
I'm pretty sure you could just delete all the jailbreak .plist files and not open any jailbreak tweaks then do a backup and you shouldn't have any traces. But I could be wrong just a guess.
I'm pretty sure you could just delete all the jailbreak .plist files and not open any jailbreak tweaks then do a backup and you shouldn't have any traces. But I could be wrong just a guess.
Those are burried deep in the phone file structure and in the iTunes backup, it might be hundreds of files, not causing any harm and not taking up much space, just leave them be, they don'y do any harm.
The icloud contact backup is the way to go, just restore and setup as new and then restore your icloud contacts.