I beleive the normal procedure in a U.S. port is to have tugs guide the ship between the berth and the channel. When the ship is in the main channel it operates under its own power.
That depends on the port and the velocity of the current of the river.
The Piscataqua River that divides Kittery, ME from Portsmouth, NH has a tidal flow rate of 4 Knots. At times that is over 6 MPH. Which makes it only second to the Niagara River in velocity in the USA.
They do not bring any ships up or down that river without tugs. Even the submarines coming into be refitted at the Naval base get assistance.
FYI, about 30 years back I was on my father in laws 32’ sailboat out in the mouth of that river about a mile off shore. Suddenly the ocean about a 1/4 mile in front of us started mounding up. A nuclear sub came up out of the water right in front of us. It was incredible and scary at the same time. Yet, I am sure they knew exactly where we were when they surfaced.