Not to take anything away from Ardour, but what you describe is well within the capabilities of Audacity insofar as preparation of audio tracks in the form of separate files is concerned. I give Audacity high marks for ease of use and intuitive GUI. It excels at using multiple tracks as input to produce stereo mixed tracks as output.
This leaves mastering as a separate question, but ALL mastering applications are happy to take audio tracks in the form of separate files as input. IMHO that is the best approach, because you need accept no compromises on either the audio editing side or on the CD mastering side.