Hello psychobunny,
With the BR1 you should be able to use the redundant SIM slot and have SIM A cut out after the 100 GB of data, switching to slot/card B. erikwong posted here showing how you can utilize the redundant SIM slot.
Because the BR1 only has the redundant SIM slot and not a second SIM module, you wouldn’t be able to use cellular bonding. It does work very well for a Hot Fail over. If you wanted to do bonding you’d need to get the HD2, or any of the Pepwave devices that have at least two cellular modules.