If you look at the rules of thumb circulating here, "50 concurrent quiz users per GB" (overhauled, Moodle 1) or "20 concurrent quiz users per GB" (more realistic, Moodle 3) you have a good chance of reaching your goal. You haven't mentioned the CPU nor the disk system. Also not what Linux distribution, which version, amoung many other relevant factors. So I am talking of the "first look".
Of course the server need to be well configured - or at least you make no blunders. For example, purging the cache before starting a quiz is exactly the wrong advice. A cache becomes useful only when it is populated! I guess your friends are Windows experts! No, if you need advice from this community, first look at https://docs.moodle.org/37/en/Performance_recommendations.