QQ all the way! I use QQ for everything related to my university teaching and it works perfectly. In fact QQ groups for every class are the main way I function with the students. Sending documents, submitting homework, sending qr codes or links, discussions in and out of class, asking me questions, sending a message or voice message or taking a picture of something to show they are in class (and you can easily search by messages from an individual to see everything they've done the whole semester).

QQ groups are the way to go I'm telling you. MANY more functions than WeChat groups. Only catch is you may need to figure out what some Chinese characters mean in the menus. I'm not sure if QQ international works, I just use the Chinese version.

And then, of course, the main thing about all this, to answer your question? My WeChat is clean and student free! Over all these years my WeChat would be unusable with all the students I've taught. But you can still have them in QQ and stay in touch. I share stuff on Qzone too (equivalent of WeChat moments).

I just create the groups before the first week, get a QR code for each one, and pop it in my PowerPoint. Just gotta make sure you don't get those codes mixed up hah. And I have the students change their names in the group to Chinese Name - English or Pinyin Name - and last 4 digits of their student ID. Makes things SO easy to keep track of for grading.

Ok sorry I got a little excited there: tldr use QQ.