1. Does the joy con grip that comes in the box need to be charged?
2. Does the dock need an ac adapter?
I think the box comes with one so I have to choose to charge it from the dock or from the ac adapter directly?
The grip is essentially a holder for the two joy con, so it doesn't charge, you will only need to charge the controllers, which can be done by simply clicking them into the console itself.
As for the dock, you would plug the AC adapter that comes in the box, then place the console within the slot to charge it. You can also separately charge the console with any USB-C cable. Hope this helps you! Happy gaming!