Hello Eric,
I've just checked and the current Thunderbolt-equipped MOTU interfaces (including the 16A model that I have, and the 828x) have Thunderbolt ports that are directly compatible with Thunderbolt 1 and 2:
http://motu.com/products/avb/16a/specs.htmlhttp://motu.com/products/motuaudio/828x/specs.htmlThunderbolt 3 controllers should be backwardly-compatible with Thunderbolt 1/2 devices, but an adapter cable is needed.
My two MOTU 16A interfaces have Thunderbolt and USB 2.0 and AVB. I currently use them via USB 2.0 (since I don't have any available Thunderbolt ports) and they manage 64 channels of audio at 48 kHz and a buffer size of 256, with no performance issues on both OS X and Windows 10, so even with USB 2.0 their drivers give excellent performance. In the longer-term I hope to get a new PC with a Thunderbolt 3 card, and then connect them via Thunderbolt, which should potentially allow slightly higher audio performance still (and up to 128 channels of audio, instead of 64). It's useful to have several connection options (USB 2.0, Thunderbolt and AVB). I don't have previous experience with PC Thunderbolt cards, but the main two current models appear to be from Asus and Gigabyte:
https://www.asus.com/uk/Motherboard-Accessory/ThunderboltEX-3/http://uk.gigabyte.com/Motherboard/GC-ALPINE-RIDGE-rev-10#ovI'm not clear whether they can work in motherboards apart from those that they list as compatible.
Echo also make an AVB interface card:
https://echoavb.com/products/streamware-nic-1... although it's fairly pricey and is limited to 64 channels anyway, so there probably isn't much of an advantage in using that compared to just connecting the MOTU interfaces by USB 2.0 for now (unless you need a very long cable run to the nearest MOTU interface) and then instead connecting via Thunderbolt in the future when you next buy a new computer/motherboard.
Hope that helps to some extent.
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.