Are these the right types of electrical connectors for hooking my Switching Power Supply up to a wall outlet?
It is okay to just use bare wires in the type of screw connector found on your power supply. They're designed for it; they have a little plate under the screw that prevents the wires from being frayed by the screw.

If you want neater wire termination, you should use one of the spade type ones. Pick the smallest size that fits your wires.

PC power cords are generally fitted with an IEC C13 plug, and those are rated for 10A (meaning also the wires themselves will be able to carry at least that much current). This is fine for any home 3D printer which usually draws a fraction of that.