That looks like a Nodemcu board, but I don't think it is. It might employ an esp8266 but I don't think it's actually a Nodemcu....Although it might be a very similar concept. I'm not sure what programming language it uses but it looks like C++ and something called a Particle IDE. (not sure what that is). Anyway, it might not be a bad solution for you if there are support resources available (forums, etc).
Yes, the esp8266/Nodemcu does use 2.4.ghz, wifi not the 5 ghz you wanted. Most routers that support 5ghz also support 2.4ghz so it shouldn't be much of a problem to configure your router accordingly. BTW, 5 ghz can support higher wifi transfer speeds, but the 2.4ghz band has a greater distance range. 2.4ghz is all I have because of the range advantage. Also many devices still don't support 5 ghz so having 2.4 ghz available may prove useful to you in the future.
Another alternative might be the popular Raspberry PI. I think version 3 has 2.4 and 5 ghz wifi, but I have not used any of the R-Pi's devices. Although I think it is vary powerful and is actually a fully functional computer system with a Linux operating system and multitasking, it even supports an HDMI monitor and usb keyboard. It's reasonably priced and a reasonably small board so using it for specific dedicated projects is not unusual. I intend to try one soon although it sounds like a bigger learning curve than a Nodemcu.
Here's an example of the nodemcu/esp8266.
http://rabbithole.wwwdotorg.org/2017/04/18/esp8266-garage-door.html
Frank