LGA 1155 motherboard works with NVMe drives.
LGA 1155 motherboard works with NVMe drives.
Inserting anything into the second PCIe x16 port will reduce it to x8. Set the GPU to use PCI_E2 and the SSD to PCI_E5, or else the SSD may not work properly.
Your NVMe adapter needs PCIe 3.0 x4. On the first PCIe 16 (PCI_E2) it will operate at x8, while the NVMe will run at full speed on the second PCIe 16 (PCI_E5) at 8x or 4x depending on the adapter. Your questions about performance impact and speed are addressed.
Up to now only the 2080 ti experiences issues when modified this way. If this applies to a gaming PC, NVMe performance remains unaffected. SATA SSDs deliver comparable results.