Optimize my MacBook pro

Yes, I have my M1. When I use my MacBook Pro for music playback I always run it on battery power/ never plugged in. I did try a USB isolator but for reasons unknown to me I could not get it to work so I returned it. I could not get any sound output. 
As far as disks, I presume you are referring to a hard drive. My MacBook Pro has an ssd drive. I actually swapped out the original ssd and now have 1 TB of storage. Original was a meager 128 GB. 
I am on the verge of seriously considering a dedicated music server with a linear power supply but I’m not convinced that it’s worth it 

Your Briscati M1 DAC (if you still have it) is asynchronous, hence timing on the computer side makes no difference.   I would try to reduce injected electrical noise, by using USB cable without +5V and GND wires and possibly use USB isolator.  You could also try quieter, perhaps linear, power supply for your Macbook.  All computers have many internal switching regulators, but I believe the main power supply affect it the most (highest power).

How is the noise out of the power supply?  Try playing while it is on and off it.  If you notice a difference you may want to switch to a linear supply.

Also, disks are so much faster and cheaper now. It won't really help your playback, but you may have a better experience and a lot more space. :)