My rule of thumb is 10^8 per second which those constraints satisfy.

This is just an estimate and depends on the algorithm’s constant factor.

I usually don’t take the number of test cases into account unless this number is quite large (1000+). In this case, I assume not all tests will have the worst case limits.

It’s more important to note that n <= 1000 and n^2 = 1 000 000 is a quite normal bound to solve a problem.