What s the best setting in GoPro hero 5 for a rave?

Auto.

There is no single "best setting".

For video, stay away from 4k. Lots of light needed, and the GoPro's small lens and small imaging chip will need lots of light for decent video quality. As it is, 1080 will be pretty hard-pressed, too.

If you need "best quality in a low light environment", then use a device designed to do that - a camcorder (not an action cam) with a large diameter lens and large imaging chip system. I use a Sony HDR-AX2000 or PXW-Z150.

The GoPro Hero 5 has an automatic low light feature. You don't have to do anything.