When the motor/dish is set up, at 0, the LNB skew is zero, then as the motor rotates, the dish turns slightly, matching the LNB skew, for each satellite, so once set up, correctly, you don't need to worry about it.
Whether you get a LNB with 1, 2, 4, or even 8 outputs, depends on you, and how many cables you require. Some receivers are capable of having multiple tuners, allowing you to record channels and still view others, on the satellite your motorized dish is pointed at. Equally you might want a feed going to other rooms, in the house, where you have other satellite receivers.
Most of this is basic, for a satellite dish, and information is available, in various guides, on the forum, or via a quick internet search.