I understand each camera may have more than one stream
ah, i thought you referring to substreams (lower rez), but you meant that most cams can support mutiple clients streaming the full-rez video.
yes, most can, but some do limit the number of connections as they don;t have enuf horsepower onboard.
Have you looked into
BlueIris (blueirissoftware.com) ? BI could pull the streams from most cameras, assuming they are reachable directly on your net.
If they are on the POE side of of an NVR, the NVR may provide an rtsp:// URL for each cam, so you'd get it from there... BI's web server will
show them all at once or grouped or individually, as you need. You wouldn't even need to record on the BI server, unless you want an extra centralized copy of everything...