I have interacted with quite a few mainland Chinese people who have moved to the West. They tend to come from well-off backgrounds since the most common way they can come here is by enrolling in a university course, which is extremely expensive. I think this + wanting to live in and fit in the West is what causes them to usually be very biased against the PRC and repeat the same propaganda lines you hear Westerners say about China (uyghurs, social credit score, etc).
Most of them are equally disappointed of what life is like in the West. Some end up going back to China, very few are actually positive and supportive towards the PRC, whether it's from a more political angle (they explicitly support the CPC) or from a more "daily life" angle (things just work and get better there, unlike in the West).