You could visit 2 following threads, s3c70r already successfully built 12 GPUs and even 21 GPUs Nvidia P106-100 in window 10, really amazing:
https://bitcointalksearch.org/topic/anyone-with-a-tb250-btc-pro-12gpu-rig-running-windows-2409330
https://bitcointalk.org/index.php?topic=2338482.20
His hardwares: Asus B250 mining mainboard, CPU core i3-7100, 8Gb RAM, set 32 Gb virtual memory, and with even cheapest PCIE to 4 extender.
Thank you for those links. I will look at them.
I will try to keep this thread alive so that I can sum up tips and tricks in the main post