If you are playing solely PCVR(from Steam) via Streaming, then there's no VIVEPORT account needed.
So, it is recommended to sign up for viveport infinity for few months, find and enjoy the content collection from infinity plan.
However, when you ends your subscription with viveport infinity, you will not be able to play them anymore unless you purchase them via Viveport or Steam platform.
hope that answers your question.