Is it possible to load balance 2 cell/sims on the GL-X3000? I only see options for it to fail over but not load balance... I also see load balance cell and ethernet
There's only one cell modem in the X3000 (although there are two SIM slots). You can set automatic failover between them - so if the connection of the active SIM goes down, it will automatically switch to the second SIM.
If you connect a second device (like tethering a cell phone or hotspot device), you can then use load balancing between the active SIM and the tethered device Actually, you can connect a device to USB, two to the ethernet ports, and one via WiFi repeater and load balance across all of them (and the built-in modem). The settings are underner Network > Multi-WAN.
Please keep in mind that load balancing isn't aggregation. Load balancing between different WAN links is mostly not recommend since it will cause many different issues. (IP changes while visiting a website for example)