Form2(0) and Form2(1).
I use this argument because variables that the constructor needs to draw (sizes and stuff) are in a array so in this way the constructor knows that for first instance he must take variable of array[0] and for second instance variable from array[1].

I'm sorry i'm pretty new in all of this so i don't know what is UI?

And for thread handling i'm not sure what i need to use for background workers because i would like if they are all 3 working all the time and every one of them is updating a different instance of Form2.The only code they are using all 3 is the code in Form2 class for the event which is drawing on instances of Form2