The short answer: Yes, the GMAT Paper Tests are helpful, but they are very old (pre-2000s), from a time when the ETS administered and authored the test, instead of Pearson Vue / ACT, and the GMAT was a somewhat easier exam (though essentially the same test, other than the extra issue essay and lack of an IR section). Perhaps most importantly, the questions from the GMAT Paper Tests overlap significantly with other official sources of questions, such as the OGs. Hence they are close to the bottom rung of the official GMAT materials ladder. And to state the obvious, don't take them as full "practice tests": a non-adaptive paper test isn't going to do a very good job of predicting your scores on an adaptive computer exam. Instead, break them into parts and try one question at a time.
That being said, they are still better than nearly any non-official sources of imitation GMAT questions, and still very useful for practice!
A quick ranking of Official GMAT question sources:
1) Question Pack 1 (my personal favorite due to the ability to create your own customized sets of questions easily, "Study Mode," which allows you to check your answers right away, and the included answer explanations)
2) Official Guides (OGs) - both paper and Wiley online versions (if you can get it to work--it's buggy). I'm a bit old-school, so I prefer paper when it comes to the OGs.
3) Default Exam Pack (contains
1,500 free questions!), Exam Pack 1, Exam Pack 2
4) The Mobile App ("The Official Guide for GMAT Review 2017" by gWhiz LLC on the App Store--not sure why there isn't a 2018 version yet.)


5) The GMAT Paper Tests
6) Old GMAT PowerPrep software
Please see the following similar thread for more help with this issue.
https://gmatclub.com/forum/are-the-gmat-paper-tests-any-good-79589.html-Brian