Two screens can share the household's network capacity while still being governed by separate account rules. A connection fast enough for both does not establish that a subscription permits both to play simultaneously.
Keep the technical and commercial questions separate. For IPTV USA, confirm the actual simultaneous-use allowance directly rather than inferring it from a term length, player feature or device count.

Establish permitted use before testing together
Ask the service operator which concurrent activity is allowed for the specific account. A player accepting credentials on two devices is not proof that both may remain active. Installation, account registration and simultaneous playback are different permissions.
Do not test beyond the agreed allowance to investigate the network. Independent legitimate sources or local test traffic can examine shared capacity without turning an account-policy question into an unauthorized concurrency experiment.
Avoid an unsupported capacity promise
A faster internet plan may help if the access link is the demonstrated limitation. It will not add account permissions or repair a distant client's weak radio. A new player also cannot establish commercial connection rights.
A useful outcome describes both facts independently: the household path sustained the tested workload, and the operator confirmed a particular account allowance. If either remains unknown, do not turn the other into a substitute or advertise a universal multi-screen guarantee.
Useful answers
Does installing the same player twice permit two live sessions?
No. Software installation and service-account concurrency are separate. Confirm the specific account terms.
Will a faster internet plan add more allowed connections?
No. It can change technical capacity, but the service operator determines the account allowance.