Having read through the first several volumes of the light novel and watched the anime twice, I'd say it's a pretty faithful adaptation in spirit but makes some expected cuts. The core plot beats of Sengoku-era warlords being gender-swapped, with Akechi Mitsuhide as a woman named Mitsuhide Akechi serving a female Nobunaga, all hits the screen accurately. You get the same mix of historical revisionism, comedy, and strategy. Where it diverges is mostly in the pacing and some side character development—stuff like the deeper political maneuvering in Owari gets streamlined, and a few smaller daimyō encounters are combined or skipped to fit the 12-episode run.
That said, the anime nails the tone. The absurdity of Yoshiharu Sagara, a modern guy, trying to survive using his knowledge of 'Sengoku Basara' game strategies while being utterly bewildered by this female-led history is perfectly captured. The crucial character dynamics, especially the slow-build respect-turned-affection between Nobuna and Yoshiharu, are intact. It's not a 1:1 page-to-screen translation, but it's faithful where it counts. I actually think the anime's faster pace works better for the comedic and action moments.