To answer your question quickly, yes, that is pretty much the standard for letters within a novel. Though, as Tave said, it depends on the publication.
There is no universal format, but there are several things to keep in mind. Any long quotation (as in a letter) can be considered a block quotation. These are typically indented, and have either a slightly smaller font, or a monospaced font as found on typewriters. It makes the letter easier to read, and to distinguish from the remainder of the text.
As for text messages, it makes sense to follow a format similar to a letter, though you could make a case for an in-line quotation due to their brevity.
Really, outside of journal publication, formatting is a highly subjective element to writing. Depending on the type of narrative, it might make more sense to try things another way. House of Leaves comes to mind, which was meant to be frantic, crazy, and frankly impossible.
If you're not trying to create anything Dada, you've hit the nail on the head.