In my experience, Kucoin has the best Customer Support. For every problem I faced, I contacted their Live Chat and got my problem solved within an hour. For FTX, I got help within a few hours. On the other hand, Binance has the worst support. It's hard to get serial in their live chat. The ticket system is also late. They take 1-3 days to response.
For KYC, my Binance account got verified instantly. Kucoin account took 72 hours.