Dear authors, in my personal opinion, war should be the continuation of politics, so political conspiracy should be the main body of the story, and magic duels should be the seasoning. However, it seems that people prefer to watch exciting battles, so I wonder how you make your choices.
This is my novel. The background is the Holy Roman Empire region in the Middle Ages. The content is that the ghost of an era awakens in a new world for some reason and begins his conquest. If you are interested, you are welcome to read:
https://www.scribblehub.com/series/2120645/empire/
In a
Historical Fantasy novel, the most important thing to me, would be the
Historical Accuracy. (It doesn't have to be perfect, but it definitely needs to be within-reason for the time period being presented).
Everything else would follow from that, but the consistency of the setting. High or Low magic. (Low would likely be better for the Sword & Sorcery feel, if you're including it at all).
The narrative, however, should prioritize historical accuracy first and foremost, otherwise it really just becomes a Fantasy novel inspired by history, rather than a historical fantasy novel.
The politics of the world should match the setting and historical time period you're seeking to depict in the most reasonably accurate sense.
The same for the inclusion of magic. If it is relevant to the narrative, then it should be viewed under the historically appropriate lens, whatever that happens to be for the time period and setting you're portraying.
I'd also like to note that it isn't even necessarily a requirement for fantasy stories to include magic at all in order to be 'Fantasy' genre, and personally I'd favor less magic in a historical-fantasy setting, but if you want to include cool powers and such, might I suggest referencing Full Metal Alchemist (Brotherhood and the original manga/novels) for what could definitely make for an interesting take on a Historical Fantasy series.
Admittedly, this is just my opinion. You do what works for you.