From what I can tell, fees are reduced if you use Binance's coin (BNB) to execute trades on Binance.  Is it worth doing this?  (I just sent some BTC over to Binance to buy something with -- should I first convert my BTC to BNB before making my purchase?)

Also, are there fees for trading BTC for BNB on Binance?  If they charge you to convert your currency to BNB, it seems like it would defeat the purpose of trading for BNB in order to reduce fees.