Maximum USB Controllers? 16?

I’ve been building the ultimate retro gaming PC and storage cabinet that emulates all popular vintage consoles, and their controllers to match. Emulating Atari 2600 through Dreamcast – half of the nostalgia-party experience is holding the authentic controller, converted to USB through the PC.

I have a Windows 10 PC and it appears I can only get 16 USB controllers to show up simultaneously in the "Set Up USB Game Controllers" window where you can calibrate USB gamepads.

I’m aware of the 4 controller limit for XInput but is there a 16 USB controller limit for gamepads? I was under the impression Windows could handle up to 128 USB devices. Windows detects these USBs as being connected, even has the alert sounds when each of them are successively turned on in order. However, they stop showing up in the calibrate window after 16. Various emulators are able to detect that "48 devices are connected" but none of them will map buttons past the 16th registered controller.

I’m looking to have all 48 controllers plugged in simultaneously so you can move from one emulator to the other without switching on the individual USB ports on the hubs. Thanks in advance for any insight, google and the like have failed me on this one. I’ve got 3 of these 3.0 powered hubs hooked up and they all work separately in iterations of 16 but not all together.