Hmm. Why is everybody assuming or wanting the Tidal quality setting to make Tidal give you a different album (or in Roon terminology, Other Version), in particular a version that does not even exist (or have been removed) in their streaming catalogue?
The introduction of HiFi Plus merely creates a lower Non-Plus price tier such that people are restricted from Master quality setting if they pay less. I claim that you get the same thing from a HiFi quality setting regardless of HiFi Plus or Non Plus subscription.
The following is what I expect:
If you choose a MQA CD album (e.g. Joni Mitchell “Blue” 16/44.1) you get MQA CD at both HiFi quality setting and Master quality setting, regardless of HiFi Plus or Non Plus subscription. The MQA CD can be decoded.
If you choose a 24-bit Master MQA album at 44.1kHz delivery rate (e.g. “2L - The MQA Experience (Compilation)”, Master quality setting gives you 24-bit and can be decoded. HiFi quality setting gives you a 16-bit truncation (aka MQA CD) and can still be decoded but with less SQ, regardless of HiFi Plus or Non Plus subscription.
If you choose a 24-bit Master MQA album at 48kHz delivery rate, Master quality setting gives you 24-bit and can be decoded. HiFi quality setting forces it to become 16/44.1 so this MQA album can no longer be decoded as MQA. (This is harder to prove.)
That being said, I’m happy to be proven wrong. I want people to have access to the format they prefer, including PCM / MQA / DSD. (But not floating point WAV, since we don’t support it. 
)