Historically correct only in the largest way. The individual details? Um, not so much.
The costumes are really not period appropriate at all and neither is the jewelry- but it is all spectacular. Sissi’s wedding dress and tiara are stunning - but not anything like her actual dress or tiaras of that period. German language (?) originally with overdubs and close captioning.
Well acted. Not sure about Maximilian’s trouble making abilities while in Austria but I do know he dies in Mexico at the hands of his erstwhile subjects after managing to get himself named Emperor there (of all places).
Sissi is lovely and spirited like I expect she would have been in real life. Franz is handsome and seemingly (mostly) devoted to her, and their chemistry is great. Sophie is not - at least yet - as sinister a force as I expected her to be but that can be further brought out in future seasons.