I can chime in with my experience from kucoin. I wouldn't recommend it unless there's smaller coins that you must have. I just recently started using kucoin and have transferred coins to it as well as have made two purchases on there. The second purchase I made still hasn't been completed and it's been two weeks. They require people to use a separate financial service for certain types of purchases.

The financial provider received my money and deposited the coin I purchased. But kucoin stopped transactions for that coin in the middle of the process so the coin is waiting for them to accept it.

It took me five attempts to get any kind of information from their "customer service" which is only an online chat. The first two times I got cut off after almost an hour waiting the first two times. The third time they said it wasn't their fault and I needed to contact the financial service. The financial service provided proof that they did what they needed to. Then the fourth attempt I got cut off again. And on the fifth attempt they said transactions had been stopped for that coin for the time being and couldn't tell me when or if it would resume.