Best way to get a video feed output from a cine camera

I am trying to output a live feed from a cine camera into another computer for processing in realtime. (I do projection mapping and vjing). What is the most effective way to achieve this ?

I looked into nDisplay, but that seems overkill, I just need a single FullHD stream.
I also tried NDI, this worked but I don’t have the settings of the cine camera (I need them to match the lens of the video projector), and the video was choppy. (And NDI uses CPU right ? I’d rather use the GPU)

Is there no way to use an output from my GPU and use a capture card on the other computer ?

I know there is compatibility with BackMagic cards but I heard it’s not working 100% and I’d need a free PCIe slot (I’m planning on an ITX build …). Is there a performance gain in using these cards compared to a GPU ouput ?

Thanks