I have two remote thermometers, a Thermoworks smoke, and a smoke X4.
I have two ambient temp probes and I've tested them in both base units and on different grills and side by side with other thermometers and they are quite accurate. What I've learned is temp can vary based on location in the pit. On my PB 820, the left side is hotter than the right, and directly over center at the main grate level it is the hottest.
On the vertical smokers, I'm not sure the best way to measure temps.
I've not smoked in a vertical, but I think I'd want an ambient temp probe (aka grate probe) on each level that I have meat until I learn how the temps vary from level to level.
As you learn your smoker, more info is good, and bad. Grate probes are just a guide. Meat probes are early indicators.
Final temp should be measured with a good instant read thermometer ( like a thermapen or equivelent ).
good luck and post some pics of your cooks.