How do you find the nth row per group without APPLY?

Short answer: ROW_NUMBER() OVER (PARTITION BY group ORDER BY ...) then filter rn = n in an outer query.

Sample solution

SELECT *
FROM (
    SELECT *, ROW_NUMBER() OVER (
        PARTITION BY DepartmentId ORDER BY Salary DESC
    ) AS rn
    FROM Employees
) t
WHERE rn = 2;

This pattern replaces many correlated TOP 1 subqueries.