RF is sometimes strange in the way it behaves - devices cannot be directly compared as two devices in the same room can be connected to different towers/carriers, or pick up on interference in unexpected ways.
Individual device antenna orientation and proximity to another RX/TX device will also affect the performance. This is not directly related, but it shows how multiple transmitters work together to shape the signal propagation pattern: https://youtu.be/49bwwQxUgcs?si=_nx35LvEzUGDfvkZ.
Making sure DeviceOS is identical will help to ensure the devices behave in a similar manner.
Regarding your usage - your account has already been unpaused until the 26th when the new billing period starts. We are not able to indefinitely suspend limits on a free Sandbox account due to usage that is beyond Particle's control. If your product is in an unfortunate location/situation where it exceeds the free 100MB limit, you will need to consider a paid Growth plan.
Data usage is driven by a device, it's behaviour, and local RF factors.
Changing the device behaviour (driven by firmware) will assist in driving down data usage.