It varies. Sometimes it follows closely, but there are some creative liberties taken to make it more appealing for the manga format.
In general, the DxD manga remains quite faithful to the novel. There might be some tweaks for visual storytelling or to fit the comic format, but the core elements and plotlines are consistent.
Not much. The Danmachi manga mostly sticks close to the source material.
The Overlord manga closely follows the original. There are occasional tweaks, but they don't significantly impact the plot or the essence of the story. Fans generally appreciate how closely it adheres to the source.
Not much. The Berserk manga mostly sticks close to the original concepts and storylines.
It doesn't deviate much. The manga mostly sticks to the key plot points and character developments of the source material.
It doesn't stray too far. The Re:Zero manga mostly adheres to the key plot points and character developments of the source material.
It doesn't deviate much. The manga mostly sticks to the key elements and plot of the original source.
The Oregairu mangas are known for their relatively close adherence to the original. They capture the essence and key plot points well. Though there could be some slight variations here and there, they don't deviate significantly from the source material.
Not much. The Dan Machi manga mostly sticks close to the source, with just a few tweaks here and there.
The manga and anime of Highschool DxD have some differences. The anime might skip or condense certain storylines from the manga.