Enpirion EN5322QI: AGND/PGND

Hello Members,

I have some questions about the PCB-design for EN5322QI:

I planning to have a PCB with EN5322QI and EN6310QI. The board will have one complete GND-plane (Layer2).

1) PGND
For me this is just the GND which I connect to the GND-plane, correct? This also means that all Input/Output caps are just connected to this GND-plane through VIAs?!
But if this is correct, why in the datasheet for EN6310QI they seperate the Input/Output caps to two different PGND pin groups? (Pin 3,4 for output caps || Pin 21, 22 for input caps)
What does this mean for my PCB-Design? Do I have to route these caps first to the pins and then from this Pin with a VIA to my GND-Plane?
2) AGND
How to seperate the AGND from PGND. On which specific point on the PCB I have to connect them together (through a NetTie?).

Thanks so far!