Does installation of Windows Updates affect the functionality of PPA service node?
Installation of Windows updates on service node should not prevent the functionality of PPA infrastructure.
PPA manages windows services via agent, which uses default windows functionality. Thus the installation of Windows updates does not affect operations of the agent.
Please note, that installation of some updates could require operating system reboot. And after reboot, it could be useful, to check that all required services is running (pleskd, IIS, Windows Firewall and etc.).