Yes you will need an aerial for the free view channels like bbc and itv, but the subscription channels will be delivered over the internet.
not if you want freeview channels
Do you receive the freeview channels in HD using an aerial when you have the TV Max HD?
Yes, all freeview channels including HD freeview channels are delivered via the aerial, regardless of what BTTV package you have.
That would depend on the quality of the aerial and the wires connecting, I've had Sky, Virgin and BTTV over the years, picture quality was unnoticeable between them.