Well if you want to capture multiple videos from a Mac and potentially mix them here are some applications to try:
- Capturesync. Best Software has this, in experimenting, it is nice because it puts all of the video into a single file. Since it is recasting files it is CPU intensive. Works fine with three uhd feeds and five hd feeds at 5 fps on a MacBook Pro (2014).
- ScopeBox. This monitors feeds and then turns it into video. This has a nicer interface, but doesn't scale beyond a few inputs and seems to hang.
- VLC. Remove audio is one important thing and VLC does this pretty easily.
Some standard dimensions:
- Logitech C920. 1080p30
- Logitech Brio. 4Kp30