I realized I missed the low-hanging fruit of a favorites list. OI veterans have likely already read all these, but worth posting in case anyone is new to the genre.
I have too many favorites to list but here are some from each category that take the cake for me.
Family: I'll Become a Matriarch in This Life
Awesome MC that does things within reason of her abilities, best father in an OI series that doesn't make his child earn his love, supportive family, and plot that keeps moving along.
Romance: The Reason Why Raeliana Ended Up at the Duke's Mansion (Complete)
Mentioned this one in the other post about sisters. Strong MC, sweet romance, a plot that reminds me of an old mystery book, art to support the mood of the series, and hilarious.
Comedy: A Single Round at Romance is Enough
You'll only like this if the author's sense of humor matches with yours. I love it. It's comedy gold how the MC is exactly halfway between being done with life and ready to live to her fullest. The interaction between the characters is fun too.
Plot: The One Within the Villainess
It keeps moving. No unnecessary filler, it's all plot. The MC is doing something every chapter towards the ultimate goal (and does it in the most badass way possible). It's nearing completion but updates slowly. I read the novel for this one and it's great to the end.
Revenge: The Villainess Reverses the Hourglass (Complete)
Up until the revenge is completed, it's high quality. After that it drags to completion since the exciting part is over. Mielle's facial expressions makes her one of my favorite villains.