If you're familiar with how that works on Android, it's really the same story here. And Swype gets smarter as you use it more and more. If it's not picking up on a certain word, you can quickly add it to the keyboard's custom dictionary. Definitely do this if "selfie" is in your vocabulary, otherwise you'll see "sulfur" pop up every single time. At launch, Swype won't be connecting to the internet to download new words or to sync your dictionary across devices; all of its "learning" is local to whatever iPhone or iPad you're using. SwiftKey definitely has an advantage there; it's got network connectivity on day one and can pull down what you've already taught the Android app from the cloud. Swype will get there before long with upcoming updates, and the team also plans to add support for more languages. For now, the aforementioned personal dictionary and keyboard themes are your main "options" to explore. The "light" theme pictured below looks way better and more at home on iOS, though you'll have to memorize shortcuts with this look since they're not displayed right on the keys.
Is Swype truly faster than Apple's QuickType keyboard? I didn't notice any striking improvements during my tests. But some people swear by doing things this way. And I regularly find myself dragging my finger around the screen on Android (though that's with Google's keyboard, which I really hope somehow makes the trip to iOS.) It somehow just feels more efficient at times, even if the gains in speed aren't obvious. Starting today, iOS users can decide if these third-party keyboards are worthy of the hype.