Ok, I managed to fix the issue with upgrading firmware, factory reset helped.
Obviously when swapping routers, I followed the 30 min rule.
Upstream Downstream
Current Rate(kbps) 6948 45730
Max Rate(kbps) 7267 45746
SNR Margin(dB) 6.3 5.9
Line Attenuation(dB) 35.3 19.4
Errors(pkts) 1 150
Upstream is a little lower than it was with W9980 (about 0.5mbps less), downstream is about the same. What I noticed is the downstream attenuation dropped to 19.4 from 23.1 but for some reason sync is the same. Strange thing is that upstream attenuation went up from 33 to 35.3 causing lower througput I assume.
The worst thing I noticed it the pings went up by 2-3ms unfortunately. It is due to different chipset in router I guess? 6-7ms previously; 8-10ms now
((
The only thing I don't like in GUI is Bandwidth Control requires rebooting the router in order to work. In W9980 I could just enable it without rebooting router.
Haven't tested WiFi on my SmartTV yet but will later. Tested it on my phone and I was shocked both 2.4 and 5GHz caught up full speed being 2 metres from the router but still. I couldn't get half of the speed on 2.4GHz being milimetres away from W9980
Will see how it goes in the next couple of days before I return W9980. I mean wifi strength, sync keeping, reliability etc.