I only use their platform occasionally, mainly to exchange crypto for fiat. I keep a very small amount of funds on the exchange, as I primarily trade on DEXs. I no longer trust centralized exchanges (CEXs).
First time I hear of someone using OKX as a fiat exchange to be honest, but if you're already using Coinbase, then I would imagine you're from UK, EU or the U.S? If so, then maybe you should look into Kraken.