The 2nd cable may improve (Scope's internal) throughput under certain conditions, but it's generally unknown when exactly and if at all.
No, it isn't
For shure more cables are an improvement in any condition and will raise the operability of a multi board setup.
Simply said a 2nd cable raises the max. possible connections inside the routing window (each cable means afair 144 channels, so with two you get 288 max possible connections between the boards).
Perhaps you know the dialogue "no more connections from board x to board y".
The reorganisation afterwards tries to optimize the dsp allocation by collecting dependant algorythms on one board and thus minimizes the need of inter-board connections.
This can be successful or not, depending on your project setup. It is more likely to fail, if there are a lot of connections and lots of devices in the routing window, but using just one cable.
Considering the limited board-connections is crucial in circuit design - especially with bigger devices, as you need to optimize the internal structure for multi-board setups (which is a not an issue for single-board setups in this regard). The STM mixers are a good example in that regard for a well optimized design. They keep the containing effects and routings on one board as much as possible and even offer a possibility to load parts on a dedicated board. This option addresses exactly the problem of not having enough connections between boards left.
Translated into daily usage this means a) to organize the project setup by keeping this fact in mind, b) to avoid too much connections in the routing window and regarding the mixers c) to connect the pyhsical I/Os to these mixer inputs, which are on the same board.
For setups containing a board with only one connector this can be always a bottleneck even leading to the possibility not beeing able to fully load its dsp due to too less channels available to the other board(s).
