For instance, I
just so I get this right- I pop the new single GPU in a Pcie16 slot, and switch its operation to half bandwith in the bios, thus boosting the bandwith of other Pcie slots? Does it work that way?You might be better offer by moving to a single GPU that has 4 outputs to save on PCIe resources.
Run it in 8X mode and that might free up some PCIe lanes for the other slots; check if the board allows that.