A load balancing router will not increase speeds. It works by trying to keep the speeds of each from dropping due to network congestion. It would send multiple web requests using which ever connection appears to be less used. I have played with them in the past and was never impressed. I also worked with a company called Mushroom Networks that allowed you to plug multiple cell cards into 1 device and it actually DID increase speeds as it could aggregate the signals but it was pricy and if 1 service dropped off 4G then none would use the 4G service. Things are likely better (and more expensive) these days.
