Hi there and welcome!
All of us electric guys use digital wireless thermometers because MES temp probes are always wrong.
You were given a great suggestion to get a dual probe version. You need a minimum of 2 probes but I will easily advocate for a 4-6 probe version as well as all those probes are super helpful to use!
So the way it works is that the thermometers come in 2 parts.
Part1: The broadcaster unit - has the temp probes that you drop down the smoker vent or just close the door on the probe wires. The probes will be in the smoker and the meat and will report to the broadcaster. You can see the temps on the broad caster AND as it's name suggest it broadcasts the temps to the hand held monitor.
Part2: The hand held controller/monitor unit - this part receives the broadcasted temps from the broadcast unit. You take this part inside with you. It also allows you to set alarms and timers and other settings for each probe that the broadcaster is running.
So you leave the broadcaster outside with probes in the smoker measuring smoker temp and probes in the meat measuring meat temp.
You take the hand held monitor unit inside with you and you set temp alarms on the meat probes to tell you when meat is ready or when to test if the meat is tender. You can set temp alarms on the smoker probes to tell you if you go over a temperature (like a flame up has happened) or if your go below a low temp (your smoker power cut off).
With the a remote thermometer you follow what the themometer says NOT what your MES control pannel says. So if your MES is reporting 300F and your themometer is showing 275F you know you are not at 300F. If you want to be smoking at 250F just lower the MES temp until the wireless thermometer reads 250F or so. That is how you will manage it.
Honestly if you have an MES hitting 300F you are super lucky because most of us are never able to hit max tem of 275F hahaha. You can always go down but you cannot make it go up :)
I hope this info helps :)