Which takes precedence: User's language setting or Company profile default language?

The mini view does not display if the record in the detail view does not have records associated with it.

If the company locale is set to US English, all users will have a default locale of US English and this cannot be changed.

A company has a custom field "Hours Worked" and the sys admin is tasked to create a validation rule so that field will not accept a negative value

Universal Container wants to prevent its service team from accessing deal records. While
service users are unable to access deal list views, they are able to find the deal records via a search.
What options should the administrator adjust to fully restrict access?