To answer your question…
Absolutely!
STEREOTYPING
When creating a backstory—although often pressured to avoid them in conventional writing—stereotypes are absolutely your best friend. As a base for character writing, they give you something to fall back on, when in confusing situations. Think of a stereotype like a hammer, although not useful in every situation, it’s crucial for any and every toolbox. They work for characters the same way.
FLAWS
The great thing about flaws is that we can take inspiration from real life! For the most part, (literarily speaking) all flaws stem from three types of character motivation; Pride, Feeling good, or the approval of others. The worship of one or a mixture of these three things can be used as a deep source of motivation for questionable actions, and can add immense variability into when and why your characters do fail.
Let’s look at an example:
Three characters, the same mistake, for three different motivations.
Telling a lie:
Character one, lies because they believe should they tell the truth, someone will think less of them…
Character two, lies because they feel the person they’re lying to doesn’t need, or deserve to know the truth.
Character three, lies because the consequences of telling the truth sound uncomfortable…
Remember: there’s no need to stick to one of these, though it’s best to start that way. A realistic character will likely swap between these three depending on traumas and motivations intrinsic throughout their arc. For example, a child prodigy, praised for their intelligence growing up, may develop a god-complex, beginning their struggle with pride. However, should they be humbled, they may over correct, becoming painfully aware of what others think…
ORIGINALITY
Go watch a movie man. Character originality is intrinsically something that has to be developed. Throughout your playtime, the character will develop through their unique responses to situations within roleplay. Don’t worry about starting off super original, that will come. Instead, draw inspiration from mashing together characters from media you enjoy.
One example of this, is my character Akiyama Yuta, as a character Akiyama is a mash of various delinquent characters throughout anime and manga, wether it be Hajime No Ippo’s Takamura, or Rokudenashi Blues’ Taison Maeda, he’s built of a combination of other characters, which developed through role-play into separate, equally interesting variants unrecognizable from the original.
Editing because I partially skimmed over the fact that these are for characters you don’t—all—intend on playing (from what I read):
Lean into other media. Taking inspiration is not bad writing, it is writing. Look at characters from the past, their inspirations, and model them after writing conventions. Remember that depth is not only lent through trauma, but also through mentorship, who your characters look up to, were influenced by, wether that be in lore, or in a meta way, through what characters you as the author based them off of. Consider them like love letters to the media you enjoy.
“Yes this brooding teacher is based of Severus Snape! I’m glad you noticed…”
There’s a reason that authors look back, because ultimately nothing is entirely original, writing is just a symphony of praise to the authors who came before you; character backstories are no different!