The data files for BRAW use 12-bit log to conserve space on your media card. When you bring it into Resolve the 12-bit log is expanded to 16bit. Any Colour processing will use 32-bit precision to compute intermediate values.
The native or base ISO for your camera is the ISO setting you can use generally to ensure you get maximum dynamic range and a good balance of stops of brightness above middle grey and stops of darkness below middle grey. Often it is best to set ISO to 800 and forget about changing it. If your exposure isn’t correct at ISO 800 you can add light or add neutral density filters to reduce light as appropriate. If the adjustments needed are small, a small adjustment to shutter angle can be a quick way to correct the exposure in camera. The latitude of the camera is quite good; if you’re not clipping highlights or shadows, you can adjust exposure in post so you don’t need to be perfect in camera. I often underexpose subjects a stop to preserve detail in highlights and then adjust as needed in post.
When shooting BRAW, you can let the camera have extra light to help with shadow detail, but try not to clip highlights where you want to retain detail. Specular highlights are okay generally if that’s all that’s clipping.