DNS really has nothing to do with internet speeds the difference in lag is measured in milliseconds not seconds, nor do Windows updates. ISPs can throttle and apply QOS methods to the traffic based on the type, VPN providers can get around this. The only issue I have seen for slow network traffic is NIC drivers and the configuration of the drivers, you can test to see if you are experiencing this problem by copying a large file between 2 computers on the same network and see what kind of speed you are getting.
Thanks to all replies to my problem. Overall, my problem is solved (for the time being) by using a different DNS Server (in this case 1.1.1.1 from CloudFlare) instead of the DNS Server of my ISP. That I believe the problem (while downloading Torrents) was (ISP-) DNS Server related is based on the correct outcome and download speed with a 3. party DNS Server (CloudFlare)! That was also demonstrated by re-use of the ISP's DNS Server which rolled back to 'throttling'! Thanks, and have a nice weekend.