How to buy BTC and alt coins on Binance?

After buying USDT via P2P, do I
(a) go to "convert" under the "trade" tab to convert USDT to BTC & alt coins OR
(b) go to "classic" under the "trade" tab, where I will be directed to a page with charts. from there, buy BTC & alt coins? Do I buy BTC only or am I suppose to buy pairs (e.g. BTC/USDT, BTC/DAI)?
what's the difference btw (a) & (b)? are the fees different too?
thank you for helping this lost sheep out!!