What else is the question you use when you want to ask about something else. Like what else do you need? What more you could use in a sentence to express something in adition as what more can I say? They can both be used in a lot of situations interchangeably. No problem. There's also the expression what's more as in besides / in addition, when you want to add some peace of information that is interesting or surprising

'What more?' is not a natural question in English. 'What else?' is.

"What else?" is the translation of "qué mas?", for example in a shop when the assistant asks you if you want another thing "What else would you like?" "What more?" would be understood but not natural in this case. "What more" is not used on its own. I can think of only one natural usage of "what more...." as part of a longer phrase.

Jack Black y George Clooney. lol