Displays and a capture card

[WalkingBread]

So i am looking at purchasing a Avermedia LIve extreme, i am a streamer who has been off for some time and awnt to change up how my streaming goes. i had a few questions on the display portion of this though. I currently have a set up with 2 computers, 1 is a laptop and the other a desktop.

 

Here is my setup

Main PC

I7 6700K with kracken x62 watercooled

2x EVGA 1080 TI SC2's

32 gigs of ram

multiple ssd's

main screen is a  samsung 43 inch 4k display

secondary screen is a benq 4k 27 inch monitor

 

Laptop(streaming PC)

I7 7700HQ

GTX 1060

12gb ram

1TB hard drive(thinking of putting a spare 480 ssd in there

second screen on this system is another benq 4k 27 inch monitor

 

So here is what i have looked at doing. i want to use my laptop to stream the video top twitch so i can lessen the load on my main PC by using the avermedia live extreme. i have tested duplicating my main screen into a 3rd output, but the problem is my screen runs 4k at 4096x2160. the other monitor i am testing this with is a 1080P ,monitor since thats what avermedia will be transmitting. the 1080P monitor scales it to 4k, but there are these huge black bars across the top and bottom of the screen. is there any way to make it so i mirror my main screen but at 1080P instead of 4k? i know my way of explaining this is a little confusing and im sorry if i cause confusion.