Can I stream via Bluetooth and use the USB input at the same time?

No. The Bluetooth and USB inputs both share the internal DAC for processing, so you can only listen to one at a time, with Bluetooth taking priority. If you're using USB for example, and start using Bluetooth, the USB signal will cut and Bluetooth will take over. Depending on your source, if you pause or disconnect from Bluetooth the speakers may automatically switch back to USB after a few seconds.