E-4B is a 747-200. The C-135 speed is for all C-135 platforms (note it is also for the much heavier E-3 and E-6A too). These speeds are for the beginning of refueling only and once contact is made, the two aircraft can (and often do) accelerate to keep the receiver above it's stall speed as its weight increases. Veteran crews can do it without any communication if needed, but last I heard, there is usually communication between the two planes either via the boom intercom or the tanker's air-to-air frequency to ensure both aircraft know what the other is doing.
BTW, I had a funny story from a guy who used to be a B-52 instructor pilot. He said that when he was doing refueling training the students would make dry contacts on legs and he would make wet contacts during the turns to keep them fueled up. He got very good at doing contacts in the turns, but before every periodic checkride he would have to do some contacts in level flight because he found that he got so used to making contact in the turns that he couldn't hook in level flight. Great to show off for the new guys, but sobering when you find out that you can't hook in straight-and-level flight.
