Jim Coroneos had books on all levels of the older syllabus, with plenty of good questions. However, the explanations were awful, IMO. The books were also very old fashioned in style (black and white with diagrams with handwritten additions, for example), but they remain a source of good questions.
Cambridge Advanced and MX1 is very much in the teaching style of Bill Pender, and it certainly is mathematically rigorous. MX1 and MX2 students who can't follow the explanations in Cambridge when first looking at a topic should look to a book with a style that better suits... but if you can't follow them even once you do grasp the theory, that is a reason for concern. If you are struggling with questions at first, Maths in Focus is suitable for easy questions and confidence building, but you need to do questions from a better source after that. The Cambridge MX1 books do have some extra questions on the Advanced topics, so anyone doing MX1 or MX2 should use just the Cambridge MX1 books and not use the Advanced books for the material at that level.
The Cambridge MX2 book is similar in style, but is written by David Sadler. Sadler and Pender worked together at SGS for many years and have similar approaches. If anything, DS wrote harder exam questions than did WMP, so the challenging material in the MX2 book is up to the end-of-HSC-exams standard.