Wasn't there also a reichstax that the prince who married morganatically had to pay to have the marriage recognized as equal. An example I'm thinking of is der Alte Dessauer who married a pharmacist's daughter (Anna Luise Föse), but the marriage was no bar on their kids inheriting. Although his eldest son (IIRC) also wed morganatically but it WASN'T equalized and the Dessau succession passed to his younger son (who married equally).
Another example is the margraves of Baden-Baden (Ludwig Georg and August Wilhelm): both married girls from noble (but not royal) families, a Schwarzenberg and a d'Arenberg, but there was never any question about the equality of the marriages AFAIK.