@Robzzz 

Hello, the tpPLC speed is not the actual speed, instead, it is the powerline link rate between the 2 adapters; the speed we can get from is about 30%-40% of it, combined with the interference, the actual speed even be slower. So compared with the current powerline rate, the actual speed is normal. 

While cause the bandwidth is 200Mbps, we can change some settings;

1. Try to change another outlets to plug the adapters. 

2. Ensure that the firmware is up to date. 

3. Try to customize the wireless settings, like wireless channel or channel width. https://www.tp-link.com/support/faq/1611/

Good day.