A correction: Thunderbolt 2 can go up to 20Gbits/s not 20GBytes/s. Thunderbolt uses a 4x PCI-E 2.0 connection.
Things like graphics cards use 16x PCI-E 3.0 at this point which is 128Gbits/s.
Things like graphics cards use 16x PCI-E 3.0 at this point which is 128Gbits/s.