Excluding steganography, an eavesdropper will know if they're unable to understand your communications. What's important is that what they can glean isn't enough for them to be specifically motivated or able to harm you.
Being seen to be using a VPN only labels you as a VPN user. In China, the authorities dislike individual VPN use, and attempt to curb it with technical measures, but for the most part, they don't go around imprisoning people only for VPN use, because there isn't much expected gain to be had from the average VPN user.
The new thing with the GFW in the last 3-4 years is to identify VPN-resembling traffic from DPI, using a fully automated/scripted system, and then over a period of several hours/days, the GFW causes incredibly high packet loss for all traffic to/from the non-china endpoint, eventually culminating in a nullroute of all traffic.
Being seen to be using a VPN only labels you as a VPN user. In China, the authorities dislike individual VPN use, and attempt to curb it with technical measures, but for the most part, they don't go around imprisoning people only for VPN use, because there isn't much expected gain to be had from the average VPN user.