• Can you limit the bandwidth / data cap per VLAN?

• You cannot limit the data for individual VLANS across a single WAN
• You CAN assign a data cap per WAN interface
  1. You will need a WAN per VLAN you're going to want to limit. This could be multiple SIMs inserted in their own modem, or a Ethernet WAN, etc. 
  2. Point the traffic from each VLAN to a specific WAN using  NCOS: Traffic Steering.
  3. Assign a data cap to each WAN, thereby limiting the LAN that its associated with
     •  NCOS: How to Configure Data Usage Rules on a Cradlepoint Router