Amount of Pies that you can create:
While M1 offers a finite amount of expert Pies based on generally accepted investing methodologies, you are able to create a number of Pies based on your own investing objectives. However, as a whole, you will not be able to save a portfolio that holds over 100 individual positions.
Same securities allowed in different pies:
Every Pie is tracked independently and the same security can be held in two different Pies. If during a trade window, the M1 trading algorithm indicates buying "Security A" in one Pie and selling "Security A" in another, the orders would be internally netted first and only the net amount would be executed. M1 will never buy and sell the same security on the same day.