I haven't tried the CVJ Mirror, but that is kinda comparing apples to oranges, since the CVJ Mirror is a hybrid, compared to the other 2 (SSR and Heart Mirror), which are single DD. The different driver types have their pros and cons.
FWIW, comparing the Heart Mirror to the Moondrop SSR:
The Heart Mirror is a neutral bright IEM. The Moondrop SSR is tuned somewhat diffuse-field neutral with an upper mids boost. Both sets have good technical performance for a single DD set, the Moondrop SSR edges it in clarity, details and imaging. Timbre for acoustic instruments is very good in both sets. The Moondrop SSR has quite bad sibilance and a thinner note weight compared to the HZSound Heart Mirror. Isolation is better on the HZSound Heart Mirror.
The Moondrop SSR actually sounds nice at low volumes, but by pumping up the volume a few dB, the 3 kHz area is shouty and is too much for me (Fletcher Munson Curve). The Moondrop SSR has very polarizing reviews, and I think this may be due to the different volumes all of us are using it at, and volume levels are typically not mentioned by reviewers or consumers. Not to mention the different sources, tips, hearing health we all have may affect our perception of upper mids/treble in the Moondrop SSR. After doing A/B testing using the same source, tips (and even cable), I’ll take the HZSound Heart Mirror any day over the Moondrop SSR, as the 3 kHz peak and the sibilance on the SSR is a deal breaker for me.
The Moondrop SSR actually has better technical performance than the HZSound Heart Mirror, but unfortunately it isn’t my cup of tea in terms of tonality.