In NuxtJS, in the configuration file, you can pass a transpile option. https://nuxtjs.org/docs/configuration-glossary/configuration-build#transpile
I don't see it impacting the final webpack file.
What does it do?
Depending of the package or the browsers you're targeting (older versions of IE for example), you may want to use Babel to transpile that into an ES5 bundle.
Most of the time it's not needed but some package require it. On top of that, the system tends to use ESM for everything so you will not use that often.