How is power divided from a wall outlet? Powering multiple motors with PSUs, extension cord
I am a little over-budget on possible output power…


No, you are way over budget on power.


You've added something up wrong. Your four power supplies sum to 1700W, not 1900W. They are completely inadequate for the aggregate load of your motors.
You cannot assume that it is "unlikely that all motors will run max power at the same time". Electric motors draw the most power under stall torque, which will occur when the motor first starts turning from a dead stop.

In the case of PSU1, this means that it will probably overload the power supply every time motor 1 starts up. You need a larger power supply for that motor.

In the case of PSU2/3, the only way this configuration would be safe would be if you had interlocks in place to make it impossible for both motors to be powered at the same time. 288W x 2 is well in excess of the capacity of those power supplies.
Power supplies are not 100% efficient. The wattage ratings you are quoting are for the output of the power supplies; the input will require more power. Read the specifications on your power supplies for details.
With regard to the extension cord… read its specifications. Any reputable cord will have its power ratings marked on it. Do not chain extension cords under this type of load.
With regard to the outlet, you absolutely cannot draw more power from the outlet than it's rated for. At best, you will trip a circuit breaker. At worst, you may cause an electrical fire.