There could be a luffy x uta fanfic where they meet in a different timeline. Uta's singing might have a special effect on Luffy, giving him new powers or a different perspective on his goals. This would lead to an interesting exploration of their relationship and how it affects the world around them.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, including One Piece, so there's a good chance you'll find some luffy x uta fanfic there.
As of now, Uta is indeed alive. The story hasn't depicted anything otherwise. Maybe there'll be changes in the future, but for now, Uta's part in the manga continues with them being alive.
Their relationship could develop through mutual respect. Luffy respects Whitebeard as a powerful and respected pirate, and Whitebeard respects Luffy's determination and potential. For example, they could start with a simple exchange of stories about their adventures at sea.
One key theme could be the exploration of the 'otherness'. Uta being a ghoul and the reader being in a relationship with him. It's about bridging the gap between two different worlds. There's also the theme of secrecy. Ghouls have to hide their identity, so their relationship might be filled with secrecy and the need to protect each other from discovery. Another theme could be the acceptance of differences. The reader might have to accept Uta's ghoul nature, with all its implications like his diet and his connection to the ghoul world.
In fanfiction, the relationship between Luffy and Law can be very interesting. They both are strong characters in One Piece. Luffy is known for his carefree and determined nature, while Law has his own cool and calculated style. Fanfiction often explores how they interact, like they might team up for some crazy adventures. Their different personalities can create some really fun and unexpected dynamics in these fictional stories.