Yes, you have to buy them (2 pieces are included).
I simply cut them open at the back and attached a clip.
That way I empty them again and again and don't have to use new ones.

The wet wiping works very well, you just have to be careful that it doesn't get too wet, but you can adjust it.

2 bags are included. Mopping goes well, you can adjust the amount of water. You can also set the direction in which the floor has been laid in the app, so the robot doesn't go "against the grain"