Lightbrite, I’m going to go out on a limb here and tell you you can eat OU products, as well as OK and Star K, as they are all reliable hashgachos. Many people will not rely on them though, and might also take the time to post here and criticize me (or worse) for telling you it’s okay to eat foods with these kosher certifications.
It would be great if you could find a Rav to speak to, instead of relying on The (Un)Official CR Handbook of Halacha. I saw your thread about washing your hands on a plane. You can get some answers here, but there are different opinions. You’ll always do best asking a Rav- you’ll get answers that are appropriate for you in the circumstances you find yourself in.