Schweser book 7 is harder than Stella. shweser book 6 is easier than Stella.
actual exam has a spectrum of its own. study provider questions involves numerous calculations. For the actual exam, I used my calculator for about 30% of the test. They are more analytical questions, and add this to the test anxiety, you can't compare the actual exam to any study providers.
That being said, practice exams are the best way to prepare for the exam. They are a wonderful source of review, so don't put them aside. do as many as possible and always go back to find your mistakes. Understand the concepts, don't memorize.