The velocity of projectile has 2 components, horizontal component vcosθ and vertical component vsinθ, where v is the velocity of projection and θ is the angle between +ve X-axis and projectile motion.
In case 1, θ = 90⁰
So horizontal component is vcos90 = 0
Vertical component at maximum height = 0
So velocity at maximum height = 0 m/s
In case 2, θ = 45⁰
So horizontal component is 141cos45 = 100m/s
Vertical component at maximum height = 0
So velocity at maximum height = 100 m/s