Avoid using the Reset functions of "Reset All Settings" and "Erase All Content and Settings" (that are in the Settings app). Because of the way the initial jail break process worked (moved various files around on the phone), tapping either of these will ruin your jail break and you WILL have to restore to iOS 8.3. So - never use those two buttons. Never.
The others are okay, but may have risks (remember, the phone's core files have been altered by the jail break).
If you are concerned about data clearing, may I suggest the free tweak "iCleaner" (recommend the default settings). It works well for me to "clean up" various files and caches.
Or, if you want to go all out, there is a program called Semi-Restore (semi-restore.com) that can clean your device to make it as if you just restored to the iOS. It doesn't remove your jailbreak, but otherwise, your phone will be as if you just jailbroken it.
That tool is pretty drastic and I've read of others having issue with it (I've never used it). Please note there are a bunch of caveats in order to use the tool (and again, the site reminds you that using it doesn't guarantee success).
But, there are some ideas to think about. Hope this helped.