I'd say it depends on how many resources you have access to and are willing to do. Checkpoints will definitely be useful, plus they contain questions that the authors have written, not just VCAA questions. I never found doing checkpoints to negatively impact doing past exams, as the study design was new last year, so the past exams did not totally correlate to the actual exam.
I found that TSSM questions were on the easy side and NEAP topic tests were more difficult. No company exam will be able to completely replicate VCAA's exams, so it's helpful to work through questions from a range of sources. A+ notes have some good stuff, but also some irrelevant things/too much detail (if I remember, it went into extreme detail for plant hormones, yet it rarely comes up on the exam).
Overall opinion- checkpoints: Yes!