In short self-resistance using limb against limb resistance, the body against an object resistance, the control and movement of one's body-weight through gravity, and moving light weights under tension. Resistance and contraction of the muscles is resistance period. The muscles don't know what is driving that contraction; only that they are being contracted. This goes back to the old Charles Atlas system of training pitting one muscle against another.
Training this way is joint friendly and develops the body from unique angles of pull. Is it superior to weight training? It depends on what purpose you have for training for weights. Your muscular development and overall strength is determined by your genetics and your ability to focus your mind to what you are doing.
Greg I know You use FMT to generalize but I think it's good for people to understand each one is differant. Self Resistance is limb against limb. Self Resistance can be done also with a stick, rope,towel, and isometric strap. With the assistance of these both limbs are involved.
Visualize Resistance is moving Your limbs with tension, plain and simple. Just think imaginary weight lifting, the practioner provides the tension. Some may know it by DVRs or VRTs. You can use light weights as a prop.
Isometrics is simple, without movement. This can be done limb against limb, isometric strap, immovable object, and bodyweight holds. If there is more pleas add to this.
Power Flexes are as a bodybuilder does, flexing. Think of a bicep curl. Curl to the top of the movement and squeeze. You must ease into it and be careful. This is a type of isometric because when You squeeze there is no movement.
What Bob calls co-contraction is actually a combination of Visualize resistance and Power Flexes. Using the bicep curl as an example. You curl Your arm up while using tension. Once You reach the top squeeze the muscle.