Workforce Planning - by employee LIMITIATIONs

Summary:

Hi All

We are planning to do Workforce Planning by employees in out of the box module?

1. Are there any limitations set by Oracle inthe number of employees that can be present in the application?
2. Can we expect performance issues if the employees are too huge ? If yes, how big is too huge for performance issues?
3. In a big organization, would it only make sense to do planning at a JOB Level?

thank you in advance