Customizing Security Roles

Is it possible to customize a security profile or group to manage contracts per a specifiic location?

For example, if John Doe is from China, can we limit his access to them to be able to manage/support contracts for that region?

AND

What about if a contract has a max limit of say $50000, can a profile dictate that they can manage it since it's under that specific max dollar limit?

Thanks!

Corey