Hi docnidi,
I am not associated with Laminar Research but I follow the comments on this forum and have my favourite You-Tube sites as well.
I understand that XP10 and now XP11 is designed around the use of 1920 by 1080 monitors and or screens.
If you have a look at the technical specifications of your graphics card resolution you will see that it is only capable of running one screen. At the best with some of the latest GTX 1080Ti cards you may be lucky with two screens linked together as one.
Have a look some of the videos at https://www.youtube.com/user/col2mab/videos?sort=dd&view=0&shelf_id=0 produced by Michael Brown. Michael is the Principal of the computer company X-Force PC, the recommended PC supplier in the USA.
In addition have a look at the following video at https://www.youtube.com/watch?v=zAVWkPp9hu0 The bottom line is you will waste your money on 4K. In an earlier posting Michael has suggested swapping your old large size 1920 by 1080 television with the new 4K planned monitor for best benefit.
There are others in earlier postings within this forum who have not had any success with 4K.
If you connect and then link your 3 screens together through the Nvidia software, on the single 1070 card then you will not need to run a second computer. The card should have sufficient screen connection points.
Hope this helps.
Glenn