I appreciate all the help,I read everything and applied accordingly. I still want to read the documentation and understand what settings affect what, in the meantime, problem is solved as follows: applied MTU of 1480 in IPv6-ND. IPv6 test website shows a result of 10/10 in an instant.
This is against the conclusions of this topic last post: http://forum.mikrotik.com/t/ipv6-mtu-problems/93243/1
Therefore, at this moment in time, if someone has an VDSL2 pppoe connection to KPN Netherlands, they need to set this MTU of 1480.
I can only mark one reply as the answer, you both have the merit! Thank you again.
