Maximum number of Bash arguments != max num cp arguments?

I have recently been copying and moving a large number of files (~400,000). I know that there are limitations on the number of arguments that can be expanded on the Bash command line, so I have been using xargs to limit the numbers produced. Out of curiosity, I wondered what the maximum number of arguments that I could use was, and I found this post saying that it was system-dependant, and that I

[Chisei]

MAX_ARG_STRLENとかlinux/binfmts.hあたり