OBS streaming from 4k

I would like to stream to some friends easily to twitch or whatever. I thought Nvidia had a way to do it. OBS is giving trouble. I'm playing in 4k, so my stream should not be in 4k because that would be impossible for anyone to watch.. does it automatically downsample the resolution? I've been trying to manually do it but the preview only shows a portion of the screen. Any ideas?

you need to set it in the setting of OBS for what you want the stream res to be.

I've set it at 720p but the problem is it's only showing like the top left corner of the screen in the stream.

ok I got it. If anyone else runs into this problem.. First set your res then right click on gamecapture, check the box stretch image to screen.