Am I correct in assuming that the information from the Joomla Content Items Overview page should be taken from the actual article and is updated if I update the Metadata Information at the actual article in Article Manager
Yes, you are correct.
For my info: these pages are imported into Joomla content / atricle items. After import the META tags are set through the SEF patch and the META data is not visible? When you do this for none import pages is this ok then?
How do you check if there are META fields set? View -> source with Firefox?