TL;DR: use a Multi-TT type USB hub.
If my computer has 4 USB ports, does that mean all I can ever hope for is 4x1100x8 LEDs?
On most PCs its even worse than that. Most have only a single USB2 controller, so when you transmit 12 Mbit/sec on 1 port the others are blocked from simultaneously transmitting.
If I use one of those ports to run a multi USB hub with ten ports does that mean I now have capacity for 4x1100x17 LEDs?
Sort of. Multi-TT hubs are the key. They let your PC send the data at 480 Mbit/sec and the hubs take care of doing the actual sending at 12 Mbit/sec.
But beware of cheap Single-TT hubs. They can only transmit to 1 downstream device at a time.
You're probably not going to get that many simultaneous streams into the USB2 bandwidth limit. But yes, within the 480 Mbit/sec bandwidth limit (fugure about 33% protocol overhead, and a max usage of 80% bandwidth), multi-TT hubs will allow efficient transmission from your PC to many downstream Teensy boards.
To get another 480 Mbit/sec, you need another USB2 controller. Even if your PC has 10 USB ports, they're probably all on the same controller and share the same bandwidth. Yes, I know that sounds very surprising, but even high end PCs are made from chips designed for consumers where low cost reigns supreme. Some motherboards do have other controller chips for some of their ports, but even on those high-end boards, you can expect many ports to share 1 controller's bandwidth!
If you add a PCIe card, it usually adds another controller, but all the ports on that are usually share bandwidth. There are some
notable exceptions, but unless are card specifically says each port has dedicated bandwidth you can assume they're all shared. Remember, USB is so popular mostly because of its low cost!
Also, USB 3.0 superspeed (5 or 10 Gbit/sec) is *NOT* an answer. There aren't any TTs (Transaction Translators) between superspeed and full (12 Mbit/sec) speed. All USB 3.0 ports and hub actually have a pair of undirectional channels for superspeed and a parallel half duplux channel for USB 2.0. Any 12 Mbit/sec devices you connect will use the 2.0 channel, either directly or through TTs in hubs. 12 Mbit/sec is *never* translated up to 5 or 10 Gbit/sec.
If USB2 is 480 Mbps, why does Paul reference 12 Mbps above? Is that a restriction of the Teensy’s USB connection?
Yes, currently all Teensy models have only 12 Mbit/sec speed on their USB device ports.
Teensy 3.6 has a 2nd port which supports 480 Mbit/sec, but currently software support is only for USB host mode. It doesn't support device mode at this time.
In the not-too-distant future (likely 2019) we'll probably have boards with 480 Mbit/sec USB device....