The Haikyu anime follows the manga pretty closely. There are only a few tweaks here and there for better animation or to make it more suitable for the screen, but the essence remains the same.
The Haikyu anime adheres closely to the manga. The characters' personalities, the key events, and the overall tone are all preserved. Though there are a few changes here and there, they don't significantly deviate from the manga's essence.
Well, you could start from the volume right after where the anime ended. But also, it might be helpful to go back a bit to get fully immersed in the story again and catch any details you might have missed before.
The ending of the Kaguya-sama anime roughly corresponds to a certain point in the manga. However, it depends on various factors like how the anime's pacing was handled and which story arcs were included. You might need to check detailed comparisons or fan discussions to get a precise match.
It's a bit tricky to pinpoint exactly. But usually, the anime ends at a certain point in the manga storyline that might not be a clear-cut chapter or volume.