Will I have internet coverage in the National Parks (Loango, Lopé) or just in Libreville?

 You must set expectations correctly. You will have reliable 4G/LTE coverage in the capital, Libreville, and the main business city, Port-Gentil. However, 90% of Gabon is remote rainforest. Once you fly or drive into the interior (e.g., to Loango National Park), you must expect the signal to be intermittent or completely non-existent. This eSIM is for cities, not for deep jungle treks (for which you need a satellite phone).