If using an Intel laptop, tools like ThrottleStop can prevent the CPU from down-clocking during intense gameplay.
Beyond DSfix, specific texture-reducing mods can help systems struggling with VRAM: dark souls prepare to die edition low graphics mod
Enabling unlockFPS 1 in DSfix can stabilize performance, but on weak hardware, it is often better to set the FPSlimit to 30 rather than 60 for a more consistent experience. If using an Intel laptop, tools like ThrottleStop