Sometimes I do this. For example my main MC for Samurai of Hyuga is based on a character in the Legend of the Five Rings book series, Hitomi was the protagonist of the sixth book in the series, and my MC for Wayhaven Chronicles is also based on a book series protagonist (won’t name this book series since this one is written by a hungarian author so I suppose that would be less known here).
Basically I watch out that I keep the personality of my MC as close as possible to the characters I make them based off. As for OOC choices: mostly I keep this to the romance area (since most already existing characters are hetero), but other than that I try to pick the choice options I think the borrowed character would make.
Sometimes I find that just as fun as creating my own character tho it’s really rare that I like a character that much and the game setting also has to have a similar vibe to the book or whatever I borrow the character from.