Will the swap fee be deducted from my sell or buy token?

The swap fee will be deducted from the token you are selling. The fee amount is adjusted from your total input, so the quote token you receive will be the remaining balance after the fee is deducted.

For example, if you swap 100 ETH for USDC and the fee is 0.3%, the actual amount of USDC you receive will be slightly less than the quoted amount, as the 0.3% fee will be subtracted from the 100 ETH before the USDC is distributed to you.