Does AFPD come with this feature "look at Ground" -a feature that will keeps the Earth in view at the bottom of the display screen in maintaining model to ground perspective.

Does any simulator have this feature? What if the plane is straight above you. AFPD has 2nd window mode that you can set to different modes including follow mode.

Also, the coming soon AFPD USB commander set, can I assume it just has all needed stuffs to plug in without any user Tx box?

Yes, that comes with a radio. If you have a radio you do not need this feature.