PCIE GPU on PCIE MOBO

There are 2 PCIe x16 slots on the T7400 Motherboard So if you only have the Graphics card in 1 of those slots then the other should be free

Is this also true of all other devices like this? I was assuming they could all reach the 1000mbs that the pcie slot could reach (plus reviews

pcie 3 slot NVIDIA NVS 510 graphics board, Full Height Bracket , Low Profile Bracket , Four locking m-DP to DP Adapters, Four locking m-DP

pcie x1 in x16 slot Supports 7th Generation Intel® Core™ Processor; Intel B250 single chip architecture; Support 2-DIMM DDR4-2400 2133 1866 up to 32G maximum capacity