You'll want to take a look at the section in the help documentation labeled, 'Advanced Variable Control (Scope)'. In there, you'll find the various ways to scope variables in VA. Variables scoped as, 'global' are shared no matter what profile is active. Profile-scoped variables are private to their respective profiles, and command-scoped variables are private to their respective commands.
On a side note, when you include commands from other profiles, you're not really running all the referenced profiles at once. Your selected profile is still the active profile with just the commands from the referenced profiles included. Two profiles are never active at the same time.
Hope that helps!