Updates on Test Data

I think the TV stream is already via igmp-v3 ,
It all points to the wifi- bottleneck, my LAN connected node makes no difference, and was not limited since ever.
At the moment, im busy with renovating the new house where i will move to, and i do not mind the quick fix. I will make a new judgement when the infrastructure is moved and running.

Do you mean Service-quality management? I have no plan where to set this up and how.
Devices are: Fritzbox7590ax(slow node via minipc on lan connected), fritz!repeater6000 (Pc with node via lan to this connected), fritzbox7490 lan connect to the MediaReciver 401.