I would like to know how many sensors can a connect to me esp8266 nodemcu, in other words how many usables GPIOs are? I understand that gpio 0, 15, 16 abd from 6 to 11 are not 100% usables... Is like that??
Depends on what sensors you are using on how many you can use.
E.g. You could run seven dht22 sensors on one esp8266-12e
So the esp12e or esp12f have 7 usables GPIOs?
I only use 2,4,5,12,13,14,16
Maybe you can use more, i don't know. I just use more esp8266's...