Joshua is a disagree along with Estelle imo. AT Delay lost it's magic after SC. Anelace shouldn't even get fielded most of the time lol
Tita is the only other "real" choice here.
I can't recall if that's the exact order, i'll look it up when i have time, but i recommend having a backup of any save files from the vanilla game. Besides that, no issues should occur.
If you are using Atmosphere to load mods it just goes it Atmosphere folder ----> Contents ----> Game ID folder ----> Romfs folder I believe.
Edit, I assume you already modded your Switch. There are tutorials out there for that.