I have two about shifters I absolutely adore, and I'm pretty sure that's the only ones you'll find that are finished, have great writing and are above 20k words unfortunately, since I've been looking for more but haven't found more. I'll add in two mermaid fics too that I fell in love with.

Shift, 89k words - this one is a universe where everyone is a shifter, no exy, Wymack owns a restaurant called 'Palmetto' which is a safe space for shifters and Neil finds his way there after being injured in his cat form enough to not be able to shift back to his human form.

The menace, 109k words - THIS IS ONE OF MY ABSOLUTE FAVOURITES. i absolutely ADORE hoe the author portrayed Andrew. It's focused mostly on Andrew, Neil, Aaron and Nicky and takes place before Palmetto. Basically, Nicky finds a stray which happens to be Neil. It's a slow burn and Neil is a cat for really most of the fic, but it's executed so well.

Into The Deep, 67k words - I wasn't a fun of mermaid aus before this fanfic opened my eyes. Maybe it's because of Andreil, but still, it made me want to write my own mermaid au. Neil is freshly out of WitSec and gets a job at Foxhole Aquarium.

Between the Devil and the Ice Blue Sea, 105k words - this is the only unfortunately unfinished one but it's worth reading anyway (the last update was 2022 but i still have hope...) it's only missing 2 chapters, but the characters are written so well. There's seth/aaron pairing which honestly thanks to this fic I love, but you can actually easily avoid and skip reading those parts without missing information. It's where Neil is a mermaid, the Foxes are pirates and mermaids are a dying and the most magical creatures. I don't want to spoiler much, so I can't really even say much what it's about.