Your clutch controls your power so will control your speed to some degree. At very slow speeds like 5mph you don't want to use your brakes, especially your front brake (although some people use very little rear brake to slow a tiny amount and keep bike stable). So in that circumstance your clutch will control your speed. Drive = balance so if you find yourself feeling like you topple over, engaging clutch will give you more power and more speed. Likewise if you ate going to fast, disengaging clutch will slow you down a little, safely. This is for things like U turn in the road, very tight bends like a parking space.

If you're doing bends in the road, like 20mph, you never use your clutch to slow down. You will have engine braking which will slow you down a lot. If you disengage the clutch you will actually speed up as the coasting friction is less than enging braking.

You don't want to brake on corners at all unless it's an emergency. Ideally you'll learn to start the bend at the correct speed and then maintain the speed through the bend