Deductions & credits

Not sure I understand your question.  But if you do a QCD the Standard Deduction doesn’t matter.  Yes the QCD comes off of your income before the Standard Deduction.  A IRA QCD should be 0 taxable on 1040 line 4b and QCD written by it.  Unless you have other 1099R taxable amounts on 4b.  So it wipes out the RMD.