Will GPU work in PCIe x8?

Hi.

I am currently setting up a new setup for vMix video steaming.

I've come over some used hardware I can buy, but want to verify that it should work.

CPU is: i7 7700
GPU is: Asus Strix 1070 8 Gb
Motherboard is: Asus Prime z270-a

However, when I look at the specs for the motherboard it is the following PCIe interface:

2 x PCIe 3.0/2.0 x16 (x16 or dual x8)
1 x PCIe 3.0/2.0 x16 (max at x4 mode)
4 x PCIe 3.0/2.0 x1

The GPU requires PCIe x16, and would normally be in slot 1

The DeckLink requires PCIe x8, and can be placed in slot 2.

What I am afraid of now is that the motherboard will degrade the slot for the GPU to be only x8 when I connect the DeckLink and will then create a great bottleneck in my system by not having the bandwidth to fully use the GPU. Has anyone any experiences with any similar situation?

However, does this seem to be a fitting spec for my application, which is to record two cameras over HDMI and stream it in HD res?

Regards

It will work, in that there won't be any problem with running the computer. Whether the performance hit will be too much is something dependent on your exact application and needs.