Question about names

[undeadrobins]

To preface this with a disclaimer: I'm very new to Chinese and Taiwanese dramas, so my knowledge is based on what I've picked up through fandom recently. However, I want to understand more, hence my asking questions! Please excuse any mistakes I make in asking!

Is there a difference in how characters refer to each other in Chinese and Taiwanese shows?

In most of the shows I've watched so far, characters refer to each other by either their full names or by honorifics until they reach a certain level of familiarity. However, according to the subtitles on Viki, several of the characters use shortened versions of names. Ah-Fei is common, as is Ah-De, even between characters that don't seem to have a particular level of closeness.

Is this abbreviated form used in a more casual way in Taiwan, or is it because I'm misunderstanding its use, or is it just poor subtitling?

Does anyone have a resource of how the characters refer to each other?

Thanks in advance!