Which DAC in the chain is playing?

Hey folks,

After owning a Hegel H190 for a few years, I decided to upgrade to an external DAC and bought a Denafrips Pontus ll (just before the price increase!).

This is my first experience with an external DAC.

If my laptop connects to the external DAC via USB, external DAC connects to H190 via XLR, how do I know which DAC is bypassed?

Should the volume control on my laptop become bypassed?

Also, I have an old Cayin CDT 15 that has an SS as well as a tube output stage. How do I know if the DAC in the CD player is being bypassed?  

Would the using the optical outputs bypass the internal DAC? 

Would bypassing the CD player DAC negate the option for switching between tube and SS output stages? 

Thanks everyone!