Your document application note document states that VMODEM has a supply range of 2.5V to 5.5V and will draw 2A bursts. Can you tell me at what voltage this 2A is measured? There is a big difference in supply design if this 2A is at 5.5V or 2.5V.
It’s measured at 3.8V - so the actual requirement is approximately 7.5 watts. Please note that there is no need for 7.5 watts on a continuous basis as these bursts are quite short (e.g. when the modem is powered-on and upon the first transmit), and we suggest that you use a Joulescope or equivalent to watch the actual behavior. The bursts are most severe if you are using GSM, and are only about 1.2A if you are using Cat-1, Cat-M, or NB-IoT. There is also a significant bank of capacitance on the Notecard to try to buffer the need of these pulses.
Hope that helps!