I have some doubts in my project please try to help me

My project is about smart monitoring plant using ESP8266 Sparkfun Thing dev as (Remote sensing unit), connected to Sensors (DHT11, Soil moisture Sensor, Water level sensor), Arduino Uno or Mega 2560 (I have doubt in which one to use) as a User application which saves sensors data and publishes data to mobile application and publishes decisions to Thing dev (Remote Sensing unit). Please clarfiy my doubt in how to connect Remote sensing unit ro user application. Thank you!

We actually have a well written project guide using the Blynk Board(ESP 8266) called “Project 12: BotaniTweeting”. I suggest you give it a read as it contains a lot of information relevant to your specific project:

https://learn.sparkfun.com/tutorials/bl … nitweeting