Add Aquitania, Imperator, Vaterland and Bismarck. The three German ships were somewhat bigger than Titanic, both in length and tonnage. Aquitania was longer than Titanic and wider, but she was of much the same tonnage. All four were a tad faster than Titanic.
All the lights would have gone out when the seawater reached the generators. The deck lights were housed in watertight fittings and would have continued to operate below water. I believe that some people reported seeing lights shining through the water, I presume that it was the deck lights that they saw.Cabin and similar lighting would have gone out as the fuses blew when water entered these open type fittings.
Bismarck was indeed a passenger liner. She never sailed under the German flag, as she was taken by Britain as war reparations and comleted after WW I. She became Majestic of the White Star Line. There's plenty about her on the internet.