On the TC4422CPA, pins 6 and 7 are connected together. On the TC4422AVPA, why are the pins not internally connected?
This is a design feature. The separated output pins allow you to have separate output resistor values for the NMOS and PMOS, giving you more control over drive-strength and timing.
Please read the "Functional Block Diagrams" in the "TC4421A/TC4422A Datasheet" for more info.