does restrict background data hurt performance of phone Do I "restrict background data" yes or no and does it have more negative side effects than positive?
Here is my phone's (Note 4 Edge) warning screen for "restrict background data".  The implication is that this is a feature meant to protect users with miniml plans from accidentally incurring charges.  It's also darn handy when travelling overseas or out of plan range.

I do not expect it would hamper performance, but may cause some functions to not work at all.