The Traktor speculation about the additional docks with GPUs is impossible, all external GPU docks you see around use Thunderbolt 3, which is based off USB-C but is improved and faster, it's 40gbps compared to 10gbps, and the Switch won't be using Thunderbolt, IIRC the nVidia tech isn't compatible with Thunderbolt anyways, so that's a no go.
Now OP's in the ballpark but he doesn't specify his calculations, here's one on Reddit that does a better job of explaining this type of performance;
https://www.reddit.com/r/NintendoSwitch/comments/5jlbub/clock_speeds_power_efficiency_and_why_the/
We'll probably be seeing closer 750 GFLOPS though (as the P1 can do that max), but time will tell. This is using a die shrink of Maxwell and not full on Pascal for a "worst" case scenario.







