XAMPP is just a package(name). Those functions are standard for Apache. Take a look there (Google). Due to lack of servers (only one for me) I never needed a balancing. Should be easy. Just a configuration. Same thing for the database system. MySQL supports it, too.
I would get some cheap WIN7 pc's to test it (Linux will do, too). Or maybe some Raspberries running Apache.
right, XAMPP is just an abbreviation for apache,mysql,php & perl. not sure what the X it must be Windows in some way since you have LAMP aswell (linux, apache, mysql & php)
he can have some testing with vmware or virtual box to create a few machines.