When trading on a decentralized exchange, such as Uniswap and Pancakeswap, all coins are in your wallet and you do not need to move them to the exchange to make a transaction, as this happens on centralized exchanges. But there are exceptions to these rules, when when trading on DEX, you will need to transfer your funds to the internal account of the exchange, for example, dydx.exchange
So now, my point is it depends on you.
You need to understand the risks and consequences of using different exchanges whether it's decentralized or centralized exchange. Because as a trader picking a good exchange is one of a very difficult thing to do.