Talking to a pair of sources that claim to be familiar with the process, the Globe reports that those staffers would imitate Trump's manner of tweeting by tossing in sentence fragments and unnecessary capitalizations. However, they do not intentionally misspell words or names. So if you see that, it's authentic.
The revelation that Trump doesn't write all his own tweets is nothing new, but the Globe report states that staffers revel in "scoldings Trump gets from elites shocked by the Trumpian language they strive to imitate," because they think that "debates over presidential typos fortify the belief within his base that he has the common touch."
Furthermore they add that there's a system currently in place where staffers bring Trump a handful of tweets on a topic with the president picking the one he likes best, tweaking it, and then sending it out.