The optimization process and recommendations:

1. Avoid Selecting Unnecessary Columns (query line: 10): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
2. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
3. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
4. Use Numeric Column Types For Numeric Values (query line: 9): Referencing a numeric value (e.g. 1970) as a string in a WHERE clause might result in poor performance. Possible impacts of storing numbers as varchars: more space will be used, you won't be able to perform arithmetic operations, the data won't be self-validated, aggregation functions like SUM won't work, the output may sort incorrectly and more. If the column is numeric, remove the quotes from the constant value, to make sure a numeric comparison is done.

Optimal indexes for this query:

CREATE INDEX person_idx_born ON Person (Born);

The optimized query:

WITH PersonSubset AS (SELECT
        *,
        ROW_NUMBER() OVER (ORDER 
    BY
        Person.Born ASC) AS Row 
    FROM
        Person WITH (INDEX (IX_Person_Born)) 
    WHERE
        Person.Born = '1970') SELECT
        *,
        (SELECT
            count(*) 
        FROM
            PersonSubset) AS TotalPeople 
    FROM
        PersonSubset 
    WHERE
        PersonSubset.Row BETWEEN 0 AND 30