The first Dark Souls PC port is notorious for being borderline unplayable with a mouse and keyboard unless you tweak the settings or use plug ins, most just used controllers for ease of use. With later versions of the game, m&k controls seem to have gotten better. Fast forward to today, most PC versions of modern soulslikes allow for both control configurations while still usually suggesting a controller.
Which do you prefer? Have you tried playing with m&k?
I use the mouse only to menu. I play mostly for PvP and it’s easier to carry a buncha shit in my inventory than keeping everything equipped and making me heavier, and changing shit out on the fly with the controller is slow.