Everything pkgx does involves initially creating package environment. It then either runs commands inside those environments or injects those environments into your running shell.
A command like:
pkgx node start
Is in fact implicitly:
pkgx +node -- node start
Which more preciselyā€ is in fact:
pkgx +nodejs.org -- node start
ā€ see
The +pkg syntax creates the package environment that node start is then run within.
In fact you can see that env if you invoke pkgx raw: