Need help! Trane ESM + z-wave questions

Hello, I am new here, not a developer.
I have two Trane Thermostats for two AC units. I read Trane manual but I am unable to figure out exactly what does ESM do. Somewhere it said that RUN is when I am home but when I go out of town or so, I should put the ESM on. If so, what is the difference between RUN with cool setting at 81 and ESM with cool setting at 81?
Also, I was given this with Schlag. We don’t pay monthly subscription after the first free year. Does that mean z-wave is not for us? What is z-wave? Is it wifi control?
There are default settings comfort and energy efficient. But they don’t tell me how it will operate. We pay 4x the cost between 3 pm and 6 pm. We keep home at 80F. I want to ensure that energy efficient mode doesn’t result in 82F or 78F as main set temperature…
Where can I get such simple user information as it is not in their manual?
Model: tzemt400bb32 with zver 2.13
Please help, Thanks!