@NikosK I know this will sound annoying and unhelpful, but are you sure you followed that guide to the letter? Starting with a fresh oc200 and ER7026? I had the exact same problem as you with having...

@NikosK you don't need to use 0.1. After you provision the router from the oc200, you change it back to 1.1 and switch the oc200 back to using DHCP.

@NikosK Try that guide I posted above. Adoption will fail claiming incorrect password if there is a subnet mismatch. You need to a follow a certain set of steps if your devices are set up on .1.x

@NikosK Try this guide, https://www.tp-link.com/us/support/faq/2983/ , it worked for me.

Mine was actually about the same. I have gigabit and it was giving me about 600 Mbps.

@Philbert duh, why didn't I think of that! Thank you, so it must be running from the router then.