At work, we got back our 0.9” x 2.0” CAT M1/NB-IoT sensor platform. We found a couple of small errors. One, the caps on the RTC crystal are the wrong value, and a missing 100K pull down on a MCU line. Other than that ok. With 6mil VIAs and 6 Mil traces, there is NO room for error. Even our JTAG connector is tiny. The modem, of course, takes up most of the top board space, but we also have components on the back side like GNSS receiver, MCU, level converter from 1.8v <-> 3.3v (modem and GNSS run at 1.8v). Fun stuff.