Short answer, yes you may charge a savings an NSF fee so long as it is disclosed. Savings accounts may be overdrawn, although it isn't a common practice because it is more difficult to make withdrawals from these. This is in part due to Reg. D. and limited withdrawals via POS, higher fees for withdrawing those funds, etc.
I suspect this may be more common if banks allow Internet banking on these accounts.
My opinions are not necessarily my employers.
Rules and Regs minus Relationships equals Resentment and Rebellion. John Maxwell