Gpu set up look like this. 1x gpu=x16; 2x gpu=x16+x16=(x32); 3x gpu=x16+x8+x8=(x32); 4x gpu=x16+x8+x4+x4=(x32). so 2xgpu=4xgpu.
So upto 4gpus can handle 1moniter but u get (x32). x16 x8 x4 are gpu slots with different speed.if u have x16 gpu card inserted in x16slot =100% ,x8 slot=50% , x4 slot=25% utilise(get speed) in the card. if u have x8 cards insert in x8slot.