I am working on a project in which I am trying to combine two seperate USB webcamera's to create a pair for virtual 360 degree footage.
Can RPi 3 encode this video and send it to a smartphone connected in same wifi network using UDP?
I remember long time ago connecting 4 webcams and streaming them in real time via wifi. But the stream was pretty slow, and it was mjpeg. Probably not fast enough to do high quality high fps streaming.  The USB buss is limited to 480 mbps (in theory). That's ALL the devices together. So two web cams and wifi. Not enough bandwidth anyway, unless if you use h264 cams.
It might be a little bit expensive, but you could run two Pis, with two PiCameras, which go right on the board with a ribbon cable and are very fast. I believe they produce h264, and can stream the video out over wifi. To save a little, a pi zero also has that camera connector, so it may be able to handle this. Two zeros ($10 each) plus two PiCameras ($30 each) still might be cheaper than two commercial usb webcams. Just a thought.