If you’re looking for legitimate guidance:
The ARM7 handles the Nintendo DS audio engine. HLE implementations of the BIOS are often approximations. In complex games that push the audio limits of the DS, HLE can result in crackling, missing instruments, or incorrect sample rates. Using the real bios7.bin ensures the ARM7 emulation is bit-perfect, resulting in audio that sounds exactly like it does on real hardware. dsi bios7bin best