At the moment, Farmbot only supports WPA2-Personal networks.
Regarding speed, 3G or 4G are not necessarily indicative of your throughput. Each generation has a ballpark range of throughput speed, but nothing is really guaranteed. That said, I doubt Farmbot consumes a lot of bandwidth, and I’m confident Farmbot would even operate perfectly fine on a 2G GPRS or EDGE connection. YMMV.
Can you explain what your Huawei device does? As I understand from your original post, the device creates a WiFi network and connects to a 3G mobile network for internet connectivity?
If so, you should first troubleshoot if you are indeed able to use the Huawei device to use the internet with the WiFi network it creates. Before hooking up the Farmbot to it, first use something like your mobile phone’s WiFi to connect to your device, and see if you have internet connectivity through its 3G connection. This will confirm the Huawei device is actually working.
After that, hook up the Farmbot, ensuring you are using WPA2-Personal security (as explained by @RickCarlino above).