Everyone is different. Some people who are non binary but lean/present as feminine might use feminine words, but others I’ve seen use the masculine because they think modifying the grammar is complicated.
I personally use the gender-neutral modified language, like using elle in Spanish.
For the languages I’m learning:
Spanish, I generally prefer terms like elle (they), amigue (friend, gender neutral), etc.
Similarly, elu with Portuguese
Dukaisms with Polish
And hen for Norwegian