This page of the user manual discusses the maximum PCIe bandwidth available for transferring uncompressed video data over Thunderbolt on macOS systems.
Thunderbolt 3 provides an aggregate bandwidth of approximately 2750 MB/s, considering overhead and shared resources. However, when dealing with uncompressed video data, specific factors such as resolution, color depth, and frame rate play a crucial role in determining bandwidth requirements. For example, a 1080p resolution video at 60 fps with 10-bit color depth and YUV 4:2:2 format typically requires around 248.8 MB/s. Due to Thunderbolt 3's shared bus and inherent overhead, the actual maximum PCIe bandwidth available for transmitting uncompressed video data may be lower than the overall Thunderbolt 3 bandwidth, possibly approaching the estimated requirement.
Precise calculations are challenging due to system-specific variables. Therefore we highly recommend to contact us when planning multi-channel ingest systems based on Mac Mini and/or Mac Studios. A general recommendation is to distribute channels over different Thunderbolt ports.