Apple has allowed iPhone and iPad users to change the default account using the default mail application, similar to the default search engine in Safari. However, with iOS 14, for the first time, users can set third-party applications as default settings for email and web browsers.
It means that tasks across the operating system will trigger third-party applications when doing things like composing new emails and opening links instead of opening the default Mail and Safari apps.
Because this is the first time Apple has allowed to change default apps for email and web browsers, there are different ways to implement this function. As noted, users can select the default application in the settings of iOS for specific and eligible applications. In addition, users can also see a unified location in Settings> General for both default options of email and web browser.
It is currently unknown if Apple will allow third-party developers to ask/remind users when they want to change their default email or web browser applications in iOS 14 and iPadOS 14 like macOS.