Question on how DAC’s work...

Hello all!

In my system, my digital sources are a Denon DVD-2900 disc player (CD/DVD-Audio/SACD) & a Bluesound Vault 2. Most of my listening these days is done with the Vault 2 streaming Tidal, especially the growing catalog of MQA offerings. 

My first question is, if I were to start using an external DAC, and that DAC does not have MQA compatibility, would I still be getting the potential of “better sound” from the external DAC even though the Vault is doing all the unfolding?

My second question is if my disc player exports SACD at a different bit-rate than what the DAC is capable of, will the DAC upscale or alter the bit-rate to get better performance?

Sorry if these are rudimentary questions, but the only DAC I’ve purchased to this point is a Meridian Explorer 2 that I’m using in a PC audio setup & was pretty much plug & play. 

Thanks for any help...Hope you’re all doing well!

Arvin