For example, if I have 100 usd worth of each X, Y and Z coin, can I withdraw only 10 usd worth of Y coin?
Of course you can withdraw any amount, as long as it's under the max limits and it's over the min withdrawal limits for a coin. Also you should check carefully the withdrawal fees for the coin you want to withdraw, else you may end up with 3$ withdrawn and 7$ fees (just an example). It may worth taking a look here:
https://www.binance.com/en/fee/cryptoFee