Thank you tom, will try the tools you mentioned later. My new USB3 card arrived today, I bought a Asus U3S6 with a PCIe x4 slot. It is using a Bridge-Chip to utilize more PCIe-Lanes than the NEC-USB3-Controller would normally and remaining full performance for PCIe 2.0. Now I can use the Leap with good performance while using Oculus-Rift-IR camera on the Motherboards USB. However, I can't notice any difference using the Rift-Hub or a direct connection. When I start the Leap-Visualizer it is about 115 fps with decreased hit in datarate to about 100 fps (but more like short stop and average framerate does not show a big impact and recovers then) in an exact 1 second interval.
PS: Tom, I have noticed drops in framerate with the motherboards usb2 sometimes also, without additional camera connected or something that could explain it.
PPS: I might should mention I am using a Rev.4 Prerelease Device. However Device FPS keeps constant 115 fps in Visualizer now, but the gaps in the Datarate fps seems like the Driver has a 10-100ms dropout every second! You can also recognize it in unsteady/jittery movement.