Currently all swaps (ERC20 -> ERC20) are done on QuickSwap using WMATIC, USDC, USDT, WETH and QUICK as possible intermediaries for the routes. Route selection is based on whichever path is more liquid.
We will soon add routing using the QuickSwap SDK and for Q1 of 2022 we will add a smart routing feature, using a service like 1inch choosing the optimal route accross DEXes.