>>I like this one but I want to avoid declaring all strings at once and then choosing (honestly I might have dozens of 20-entry arrays, I'm not sure how many arrays I will need yet).

If all the strings are hard-coded in the program, they take up the same amount of memory wherever you put them. The compiler will put all those strings into some (probably) read-only memory block, so your concern is a non-issue. Probably a better solution is to put the strings in a text file then read them into memory at runtime. you can create a text file similar to standard ini file
your program will look for the tag it needs then read the strings until ene-of-file or another tag name is encountered. This method gives you a lot more flexibility because you can freely add more strings to the text file and not worry about adding/recompiling your program.