If I am going to stream a song over Bluetooth is a DAC going to make sense?
If you can get a solid connection going with one of the better codecs, like for instance LDAC, then I don't see a downside.
But then again, the old apX codec isn't obnoxiously bad? So, if you already have Bluetooth reception as a feature on your gear, the answer might be... 'no'(?). I guess it depends on what criteria must be met for things to make sense to you
I assume the DAC should be after the Bt transfer...
Correct. Also, a lot of DACs have a Bluetooth reciever built-in.