They’re not all that comparable honestly. The Cloud Mix is a combo BT headphone and wired gaming headset, whereas the Opus is firmly a headphone, and a noise cancelling one at that. The Opus mic is made more for phone calls and not gaming. I try not to compare proverbial apples and oranges too often because they’re meant for different users.
The Opus has an excellent, neutral sound signature and wonderful ANC. The Mix has a warmer bass rich sound and a dedicated boom mic. I personally think the Opus sounds much “better” from a critical listening standpoint and I’d also prefer it for my own gaming listening but that’s because I like a flat/Harman target style sound.
Again though these are two rather different products. Need ANC and a flat, accurate sound? The Opus is the only choice. It’s like a combo of a Bose/Sony wireless pair and a studio model. Need a lightweight portable wired gaming headset with HyperX’s slightly warm-but-still-great signature and also a BT mode? Get a Mix. It’s like a blend of a Cloud Alpha and a Beats/style headphone.
I usually only write full comparisons or try to decide what’s “better” if two products are in the same market category. These are both really good at what they do but they do different things.