Yeah Atmos overrides any balance control because that’s the whole point, Atmos is mixed with certain things sent discrete to individual channels at the mixer’s discretion and it would be very resource intensive to take a minimum 7.1.2 mix and make it pannable in the space. But yeah do try out the Atmos test tracks and that should isolate most of the speakers, here’s one:
https://tidal.com/track/243820594
As others have stated, Atmos tracks are mixed selectively and do not always just send things to the height, woofer and surround channels. That’s up to the mixer who engineered it. Most audio engineers I know tend to use surrounds/height for room reverberation effect to make it sound more naturalistic, and often use the center channel for vocals more than left/right.
Also are you sure you’re subscribed to Tidal HiFI Plus and that you’ve turned that option on in the car? Tracks that will instantly make the surround channels noticeable are Prince’s When Doves Cry Atmos Mix (the opening guitar spins around the surround speakers, Princes lead vocal is cleanly isolated to the center channel with backing vocals spread wide) :
The Doors Riders On The Storm (sounds like you’re in the studio with them, and the rain storm makes excellent use of height and surround channels):
https://tidal.com/track/126176118
And here’s proof the Lucid has enough bass, INXS Mediate (in Atmos you can mix a discrete subwoofer track and this definitely has discrete LFE elements):
https://tidal.com/track/222435050