14 sensors is far more than a single NodeMCU ESP8266 can handle. If you choose the NodeMCU ESP8266, you will probably need three of them.
If you have the ability to run Cat5 Ethernet to your Alarm Panel, you might want to use an Arduino MEGA 2560 + W5100 Ethernet shield. This will allow you to connect everything to s single board.
The third option is that you could use a NodeMCU ESP32 based board. The ESP32 has a lot more I/O pins than the ESP8266. I believe you could almost get everything connected to one ESP32, but maybe not quite. Also, the ESP32 is newer and less mature than the options above, so proceed with caution.
At least these are all very inexpensive options, so it’s not like you’d be out a ton of money if you had to change.
It is probably best to post new questions regarding ST_Anything in the more active and current thread at
Finally, have you looked at Konnected? Konnected is a purpose-built alarm panel integration for SmartThings. Not sure if they have their version ready to allow you to leave the current panel in operation though. I know they were working on a solution. If you haven’t taken a look at Konnected yet, it may be worth your while.