A PCI-E 4x4 card would run on gen 3 at x4, cutting performance in half from a gen 4x4 connection.
CPU is not quite as critical for 1440p under 120fps. At 4K the CPU is almost irrelevent. There will be a difference from CPU but single but not a visual difference if it’s at least on Haswell or Coffee Lake
A PCI-E 4x4 card would run on gen 3 at x4, cutting performance in half from a gen 4x4 connection.
CPU is not quite as critical for 1440p under 120fps. At 4K the CPU is almost irrelevent. There will be a difference from CPU but single but not a visual difference if it’s at least on Haswell or Coffee Lake