What is correct ? Both (general )is fine , or Both are fine ?

ARE. In the case of NY vs LA, you are still talking about two things. Anytime you use the word "both," it always refers to two things, so you always use ARE.

It depends on what you mean.

"Both are fine" means each girl is feeling fine, or going to New York OR going to L.A. would be fine. It's plural because it's referring to two things separately -- each, by itself, would be fine.

"How are the girls today?" "Both are fine."
or
"Do you like New York or L.A.?" "Both are fine."


"Both is fine" means doing something with both girls TOGETHER, or going to New York AND L.A., would be fine. It's singular because it's referring to two things as a couple, and you can't separate them.

"Should we talk to one girl, or both of them?" "Both is fine."
or
"Would you like to go to both cities, or neither?" "Both is fine."


I hope I haven't confused you worse, singular vs plural can be tricky.

'Both' implies two. it is always plural.

Amora Rosalind- 5 Callista Grayce- 7, I would like it better with one L. I know a Calista Jenae (Cali J) Honora Jean- 1 Katarina Isobel- 8, I like it. Meghana Elizabeth-2, Meghana is too weird for my taste, sorry. Rhiannon Madeleine- 3 Vivienne Claire-9, My Favorite :) it is so beautiful Wilhelmina Frances-2, not very pretty in my opinion Antonio Jacob-5 Beau Isaiah- 4, The only reason i don't like Beau is because it is a word not a proper name. Ethan Gabriel- 8 Finley Martin- 6, not bad actually Joaquin Elijah-2 Matteo Joseph-3 Nathaniel Henry- 6, I could flow better with a different name Sebastian Elliot-9, I love Sebastian Wilhelm Jonah-2 Fun:)

what if the subject is uncountable

Technically, "both is fine" has the correct subject/verb agreement. However, "both are fine" is also correct and more commonly used.