Cutting the wing span and area could increase the speed in the straight away. If you are going to decrease the wing area it will be far better to decrease the chord rather than the span because that improves both the straight away and the turns.

Chopping the wing tips off will have a very detrimental effect in the turns because the plane can't turn as tightly and because it will have more drag in a wider radius turn than it did before the change. Not only will the induced drag in the turn be seriously increased but the induced AOA will be seriously increased which in turn will seriously increase the fuselage drag. Not only that but it will be in the high drag state longer. What is the frontal area of the fuselage when it is at an 8 to 10 degree pitch up compared to the frontal area of the fuselage aligned to the direction of flight?

BTW, the power off glide angle is not much affected by wing loading. Increased wing loading increases the sinking speed and the horizontal speed in the same proportion. Cutting off the wing tips degrades the lift to drag ratio and steepens the glide angle because of increases in drag, not because of increases in wing loading.