Thunderxxx er um... Thunderbolt latency?

I found this interesting statement:
"More Money For Lower Latency
Another way to minimize latency, if you record bands and musicians frequently, is to get one of the newest Thunderbolt interfaces that can provide under 2 msec true round-trip latency. This will cost you quite a bit since you also need a computer capable of using Thunderbolt, but if it’s your business to record bands, it should pay for itself quickly."
 
https://sonimus.com/home/entry/tutorials/58/audio-latency-tutorial.html
 
I am at a loss to figure out how the admittedly somewhat faster connection speed compared to say USB 2 is going to produce a massive decrease in the usable latency. My understanding is that transmission speed is generally a minor factor in the total latency issue. 
 
Thanks for the correction abacab

The best USB-2 audio interfaces yield rock-solid total round-trip latency of 4.3ms (48-sample ASIO buffer size/44.1k)
 
With Thunderbolt, you can achieve PCIe level performance.
This doesn't translate into more processing power (DSP) for EFX.
I've compared performance of the Lynx AES-16e vs. RME Fireface UFX (side-by-side). 
Using DAW Bench, the machine could run the exact same number of plugins with each interface.
 
The main advantage to PCIe is that you can take the ASIO buffer size down to 32-samples (some even allow going down to 16-samples).  At that point, you're at 2ms (or below) total round-trip latency.
To effectively work at these settings (especially with heavy loads), your machine will need to be a monster.
 
If you think Cubase 9.5's Audio Performance meter's "Realtime Peaks" go crazy at a 64-sample ASIO buffer size, wait till you see the ballistics at a 32 or 16-sample ASIO buffer size.   
 
Thunderbolt provides access to the PCIe bus.
Under ideal circumstances, you'll achieve PCIe level performance.
Think of Thunderbolt as "external PCIe".
 
The only real advantage of Thunderbolt is the ability to achieve sub 3ms total round-trip latency.
If that matters to you, Thunderbolt (or PCIe) is the solution.
Note that the Apollo series (even though great interfaces) offer about the same round-trip latency as the RME Fireface UFX (USB-2)... due to the onboard DSP processing capability.
 
If you're looking for sub 3ms total round-trip latency, the Presonus Quantum and MOTU AVB series (connected via Thunderbolt-3) should be on your shortlist.  Note that you'll also need a Thunderbolt-3 (USB-C) to Thunderbolt adapter.  Apple makes one for ~$50.  We've had very good luck (testing under many different circumstances/machines/etc) with the Apple adapter.
 
 
 
 

There are still some issues regarding PCs and Thunderbolt from what I've been reading...because in PC land a Thunderbolt port is usually labeled USB c 3.1. Whilst, from what I read most of the thunderbolt interfaces will work with PC thunderbolt, there may be some compatibility issues. I've done some research - not enough to be certain. I'm hopeful of getting one later this year.

One of the exciting prospects that thunderbolt offers, is the ability to use virtual effects - guitar rig for example in a live situation. Finally freeing us from DSP cards and interfaces. This is what I'm most excited about mostly.