Whats in an icloud backup
Provided that you have made a backup of the data you want to keep via iTunes or iCloud it is safe to restore your phone from an old backup and later restore it to its present state from the backup you had made.
I would suggest using iTunes just because it seems more convenient to me and so as to you would feel safer about your data- an iTunes backup holds all the information necessary to restore your phone to its state at a set point in time.