I just grabbed Wavelab Pro today & was glad for the CC121 integration. I had a Cubase project open, exported a clip, opened it in Wavelab (with Cubase project still open), and hit play on the CC121. Wavelab AND Cubase both started playing. Both apps respond to CC121 messages simultaneously (EQ2 gain in Cubase zooms waveform in Wavelab, etc).
Issue 1: I cannot see how to force CC121 to work only with the focused app. Options for this device in both apps are minimal.
Issue 2: I hear the audio from both apps (I have Wavelab set to release driver when in the background - I also tried the other option “release when Cubase / Nuendo is in foreground”).