If I disable a Windows task in task scheduler will it stop the current task that's running too?
If you disable a task while it is running it does not stop the current execution, the current process will continue to run until it finishes.
Just all next scheduled executions will be disabled.
If you run a task manually and don't want it to start again automatically while your manual run is still processing, you can setup the task to apply the rule "do not start a new instance if the task is already running" (however, this is the default config when you create a new task).