Kinda an old comment, but no.No - PCIe allocates dedicated bandwidth based on directional lanes.
For PCIe 2.0 it’s 500MBytes/sec per lane, per direction. For full duplex single port 10GbE you need 2 PCIe lanes up, 2 PCIe lanes down (x4). If you need dual port 10GbE it’s either PCIe 2.0x8 or PCIe 3.0x4 (985Mbyte/sec x4). In other words, install a SFN5122F into the 5070 big and it’ll work more like a 5GBps dualport.
PCI-E is Full Duplex, a 1x lane has two data transfer pairs four data lines total.
2.0 x 1x will give you 500MB/s in both directions at the same time.