Gigabit powerline is similar like WiFi. It transmit signal frequency over power line instead of over the air. IF the signal is bad, the speed still get degraded. It depends on how many joins the signal goes through other than the resistance and interference in AC power line, but it is still worth trying I guess.

Your TV support 802.11n which is about 450 Mbps, by which I would say around 225Mbps. Even if you connect through 2.4GHz under 54Mbps, it still enough to stream the UHD video which require 25Mbps (recommended). You are not going to stream 2 x UHD video simultaneously, right? Well, this 54Mbps bandwidth is your LAN (assuming not sharing with other users in the house). So, there ia no interference. Your broadband of 100Mbps is between your BTU and service providers. Just consider the other 50Mbps is for other users on the other WiFi router.