Yes, pip is an essential part of the Python packaging ecosystem, and a must-have. It is also used by deploy-ng to grab prebuilt packages of Panda for different platforms (as a replacement to the old runtime.panda3d.org package system).
For clarification, --wheel builds a .whl file, a binary package that “pip” can install. It is also used by deploy-ng at build time, to pull files from that are shipped with the game (deploy-ng can be configured to read .whl files from a directory, or pull them from archive.panda3d.org/branches/deploy-ng )
Note that if you are going to do development, it may be easier not to install Panda at all, so that you don’t have to reinstall it whenever you make a source change. You can use Panda directly out of the build directory by configuring your shell environment. You can simply set the PYTHONPATH environment variable to the “built” directory that makepanda generates and add the “built/lib” directory to the LD_LIBRARY_PATH, and the Panda build should be fully functional from the Python prompt.