Those render settings are document properties, aren’t they? So it will depend on whether you import or open. If you import your default template settings are used and those are probably reset to the correct settings but when you open a obj file I’m not sure which template is used.
If you drag an OBJ onto a file, it should not reset or affect the render settings in any way. So the behaviour will depend entirely on what file you had open before you did the dropping.