Creating a new yargs parser object to get the terminal width does not seem the right pattern to me.

(I am guessing you decided against using yargsInstance as the variable name. It isn't used elsewhere in this file so not an established pattern.)

y is used in this file in a few places where a variable is used for the top level parser:

const y = yargs(process.argv.slice(2));
y.version('1.0.0');

Following that compact pattern, how about:

Use y.wrap(y.terminalWidth()) to maximize the width of yargs' usage instructions.