M2 card reset pin is active high and you need to hold the line high for 100ns min after power supply has stabilized

SPI on RG1xx M2 is slave mode only

The Sentrius M2 Card's SPI logic level is at 3.3V.
 

This is an output from a GPS module on the RG1xx. The 1PPS is a standard output from GPS modules. Currently GPS is not supported on the RG1xx.

PIN 71 is an input to the RG191 and is the reset  for the SX1301.

Pin 41 is used to identify the type of M.2 card.

The Connector for the RG1xx Concentrator Card on the Sentrius RG1xx is a standard PCIE M.2 Key connector.
There are various suppliers for these connectors but the Sentrius Gateway uses a Kyocera, Part# 24 6411 067 401 894 E.

Generic ECAD Models can be downloaded from Mouser

Yes, as long as they are operating on different networks such that AS923 sensors talk to the AS923 gateway and vice versa for AU915 devices. 

No, an RS1xx AS923 sensor will not work with an AU915 gateway because it cannot receive the downlink packets due to differing bandwidth and frequency plans used and therefore will drop off the network.