Internally we refer to variables as Global Variables as they are shared across the system including rules and dashboards. So yes, changes from rule A will be visible in rule B.
Can you share more details about what you’re trying to accomplish?
One ‘gotcha’ with this is when using a variable as both a trigger and top-level condition within the same rule. In that case, make sure to use Context Variables ($context.event.value), as it’s possible for the event to trigger the rule before the variable is completely updated in the database.