With unicast delivery, each client receives its own stream connection. Multiple household screens therefore add network demand even when they show the same programme. The service's simultaneous-session allowance remains a separate account rule.
Count active playback
A player open on a menu may behave differently from one actively decoding video. Close sessions you are not using and follow the provider's definition of an active connection. Device installations alone do not describe real traffic demand.
Plan the household capacity
Add the likely bitrate of each active stream and leave room for other traffic. The total varies with quality versions and adaptive behaviour. Do not assume that two screens showing one channel share a single internet transfer.
Distinguish provider IPTV arrangements
Some managed television systems use multicast within their own network. That does not mean an ordinary internet player uses multicast. Use the actual service documentation before applying router settings intended for a different delivery model.