It seems very rare for the vendor to specify the range of movement on a web site - you only really know once you test a particular model. By the sound of it, you've discovered by experiment what the range is for that particular servo - there's no compatibility issue as such, they just have 160 degrees of motion. Some models will have more, others less.
The arduino can't supply enough power directly to run multiple servos; depending on the model, it's generally marginal to run even one - you need a separate power supply - connect the grounds.