That's a good point. I should say I've only seen the "low quality" counterfeit money once. The one I saw had similar texture as real money, but the paper was either thinner or thicker than the real one. I can't remember the details since it happened years ago.

There is a metal strip in the real 100 RMB notes that most of the copies don't have.

You can crinkle the paper money in your fingers. Real money makes a unique sound. It is perfectly acceptable to test the money in front of the person you got it from.

I had to use cash instead of WeChat a few times and the vendor also did this as a test.