To limit access to a field see acf/prepare_field. In this filter you get can wp_get_current_user(), check if the current users access level. Return false if the user should not be able to edit it or return the field if they should be able to edit.
There is no solution for “bulk editing” user fields. In fact, there is not a currently supported solution for bulk editing acf fields. The best advice I can give here it to use WP All Import/Export Pro with the User add on. You could use this to export users, edit values in a CSV and then import the updated values.
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