Alternative: Grove Indoor Environment Kit for Edison if you're budget conscience
Controllers and Shields
The Bluno is a great way of transferring data through its apps of sensor readings. Its not too expensive and provides much more utility than a normal Mega. The only reason I am not using it is because the need of a mountable case.
The WiFi controlled relay makes this an IoT project and it works great. The only downfall of the relay is that it requires a LAN cable hook up. There are now true WiFi relays on the market but I haven't gotten the opportunity to use one yet. If you chose this option you will need a LM7805 however they heat up rather quickly so you either want a Murata 5v regulator or a large heatsink for the 7805 or perhaps they have a 12V flavor now. I have a video of the WiFi relays in use but for now Im going for the much cheaper IR Relays.
Remove the adhesive backing of the LED strip and lay it out around the top perimeter. Drill of the greenhouse making sure the power connector is near where you want the terminal block/power distribution point to be.
Next you will want to place out the sensors and components on the greenhouse to your liking. Just lay the greenhouse on its side and populate it. Something to consider is that you have 2x 50CM cables which I like to reserve for the soil moisture and the temperature/humidity sensor since you would want it placed away from the ventilation fan. Make sure you have adequate slack for all sensors.
Once everything is placed you can mark the holes with a fine tip sharpie or hold onto the sensor and drill through the mounting holes. Either method you go with you will want to drill out the mounting holes on the sensors ever so slightly. I included a picture of how finely I drilled out the holes. The mounting holes run on the tight side making even .5MM off too tight to mount without bending the sensor board.You do not need to do it to all mounting holes, just enough so everything fits without bowing. Buy M2 stand offs and screws for these sensors while using M3 for the Arduino itself.
The 1/2" holes on the greenhouse walls are for routing the grove cables from the interior sensors to the exterior Arduino Mega. The holes can be any size but just make sure it is enough to get the connector head through and without nicking the wire when it is being pulled through the hole.
Lastly for the fan, I did not have much confidence in myself to dremel out a perfect circle for the air flow so I just made multiple 1/2" holes to accommodate the airflow and it works just fine. Not an overwhelming amount of wind, just a gentle breeze.