1. Personally I support always the older name, because is the legitime. Many botanist described Narcissus miniatus before, under other names and it seems Haworth is the older. But all these names were not accepted considering it was in fact Narcissus serotinus L. somthing really not incredible because they are completely different geografically, anatomicaly and genetically.
Everybody can support the name he considered more legitime, but N. miniatus is the newest from a log list of names.
Narcissus serotiuns L. in Europe only grows in Portugal (Algarve) and Spain (Huelva, Sevilla, Cáceres and Badajoz).
If you want to recognize both species, I would think:
Mediterranean element--> N. obsoletus
Atlantic element--> N. serotinus
Orange corona--> Narcissus obsoletus
Yellow corona--> Narcissus serotinus
With a leave when blooms or not-->N. obsoletus
Without leave when blooms---> N. serotinus
One or several flowers per scape---> N. obsoletus
One flower (rarely two) flowers per scape-->N. serotinus
Perianth tube without segments, narrow--> N. obsoletus
Perianth tube with segments, like a wine bottle---> N. serotinus
Genetically, they are also different and some authors suggest Narcissus obsoletus has a hybrid origin,it would be a successful hybrid between N. elegans and N. serotinus. The sterile hybrid was also called N. x obsoletus and more recently N. x perangustus.
It is also interesting to say Narcissus obsoletus has much variability:
Greenish tepals (called var. fallax)
Narrow tepals (var. oxypetalus)
Peach tepals (collected by K.G.N)
And also another variety var. intermedia, that some people considered as an hybrid between N. serotinus and N. obosletus. This is interesting to me, because I consider N. serotinus is uniflower, but there is a region between Cordoba and Sevilla where there are both species and intermediate plants.
2. Yes, the hybrid is in both countries, and there is probably an hybrid between N. serotinus L. and N. viridiflorus in Morocco, but not in Europe.
This year I would like to find N. viridiflorus x N. cavanillesii, but finally I couldn't visit Cadiz...