You get the raw file either way and even if you only shoot raw you still get a JPEG. The camera is going to create the JPEG whether you want it or not because it embeds a copy of the JPEG into the raw file.

If you shoot raw + JPEG the implication is that you want the JPEG and should then expose to get as good a JPEG as possible. This will typically compromise the raw file to some degree as the exposure that creates a good JPEG is most likely reduced some from what you could apply to the raw file.

With digital sensors more exposure equals better image quality. However too much exposure nukes your highlights and your dead. It's kind of like playing chicken with a concrete wall. You want to stop as close to the wall as you can but never hit the wall. The camera engineers know this well and so when they adjust the software in your camera that creates JPEGs they tend to be conservative chicken players and they stop well before hitting the wall. You get a good JPEG and certainly a usable raw file.

But knowing what I just told you it starts to nag at you that your raw files could have been exposed more and would be just a little better. Most of the time it won't matter but then you eventually take a photo in which a little more exposure to the raw file really would have helped. Then you start considering just how good at playing chicken you can get and you start creating better raw files and bad JPEGs. Then there's no sense in creating bad JPEGs so you stop bothering.

You have a Nikon camera and Nikon's engineers play a pretty mean game of chicken. They cut the difference pretty close. This situation varies one camera maker to the next. I have a Fuji camera and they're as scared of that concrete wall as Trump is of an angry black woman. So if I expose to get a good JPEG with my Fuji my raw files are often underexposed by half of what they could be. I don't bother then to save the JPEGs since the exposures I set typically blow the JPEGs.

The moral of the story then is to a greater or lesser degree depending on the camera brand you can't set a best exposure for both the JPEG and raw -- you gotta pick one.

Joe

When you become a RAW photographer, you become the decision maker for these considerations in post processing, where many had been decided by the camera for the JPEG:

1. Sharpening
2. Noise Reduction
3. Color Saturation
4. Exposure adjustments, general
5. Contrast, general
6. Highlights and shadows
7. White Balance
8. Lens corrections
9. Color space
10. Pixel resolution for target image share platforms

You don't have to understand all these issues, but when you do, you'll be much more successful as a RAW photographer and you'll begin to find your JPEGs are worthless.