Yes, commissions on various exchanges differ from each other. Two days ago, I had to withdraw Ethereum from the Poloniex and Binance exchanges. At the same time, the Commission with Poloniex was 0.01 ETH, and with Binance 0.004 ETH. But on the same day, the Commission for withdrawal to Myetherwallet.com it was even higher than on the specified exchanges.
Yes, that's exactly what I meant, there are big differences between the different exchanges and I don’t know why, at least on Myetherwallet.com you can control the fees somewhat as you can reduce them by reducing the gas required for the transmission, but in Poloniex and Binance exchanges these fees are fixed and cannot be Control it and it should be paid in full.