Multi Saving in Photoshop Raw

Since you're posting in the Photoshop forum instead of the Camera Raw forum, it will help for you to please clarify:

Are you editing the images in Adobe Camera Raw, then opening them in Photoshop and running a Photoshop action that saves them to JPEG?

…or…

Are you editing the images in Adobe Camera Raw, then staying in Camera Raw and using its Save button to do the bulk export to JPEG?

There's no option in Photoshop or Camera Raw to control how many images get processed at once. It will try to do as many as possible at once, because in the past, users complained that the program wasn't using all of the available power of their computer to finish faster. So now it does.

There are ways in macOS or Windows to control which applications have CPU priority. But since those methods are kind of technical and I've never tried them, if you want to go that route you can research it. For example, you might try using the nice and renice commands through the macOS Unix Terminal. I don't know how much difference that will really make.

I agree with Michael's response that I am not 100% sure of your workflow. When you batch process images it will work through the entire process until complete, but you have the option to select smaller batches to process. However, this will mean that the process is not 100% automated.

Depending on your computer setup, dedicated RAM, video card..., you might be able to speed up the process.

Sometimes it's best to let Photoshop do it's thing and grab a cup of coffee

I don't follow your workflow 100% but is the main issue here that the processing of RAW files is preventing you from continuing to work in Photoshop? If this is the case you should know that you can also edit images in Camera Raw through Bridge. The cool thing about this method is that this version of Camera Raw is independent of Photoshop. You can thus be processing a bunch of images through Bridge while doing something different altogether in Photoshop. Just a thought.