I am trying to simulate a 12V LED strip as per this tutorial. However the schematic I tried to make on EasyEDA looks quite different from the images on the website. I wanted to know if what I did is correct.
Schematic and wiring diagram are not the same. They seem to use different RGB LEDs. The wiring diagram has common anode RGB LEDs, while your schematic uses a common cathode RGB LED. The difference is, which side of the LED gets switched.
In the common anode configuration, all anodes (positive lead) of the individual color LEDs are connected together, while the cathodes (negative leads) are brought out, so that you can switch them via the MOSFETs. That means, that the MOSTFETs are connected between the strips color component pins and ground.
In the common cathode configuration, all cathodes (negative lead) of the individual color LEDs are connected together, while the anodes (positive leads) are brought out for you to switch them. In this case, the MOSFETs are connected between the strips color component pins and Vcc.
Besides that, you should be careful with providing 12V at Vin of an Arduino Uno. While it is possible, you can very fast get the linear voltage regulator to overheat, when providing 12V. It dissipates the excess voltage (so 7V, to get it to 5V down) as heat. The voltage regulator is not cooled, so you might run into this issue, with the wiring diagram. It depends on your much current you draw from the regulator.