Will E-Invoicing and Direct debit payment increase Accounts payable efficiency ?

No, basically by E-Invoicing and direct debiting Payments, your efficiency to Hold Payments upto last day reduces, which effects on your overall balances.

E-invoicing and direct debit with adequate controls in place will increase account payable efficiency

Definitely E-Invoicing and direct debit payment will increase the efficiency of AP majorly in terms of TAT of manual process of invoicing and payment.
However, it will require great controll system to have a error free smooth process.