Just a handy notes for Juniper EX Series Switches the cable layout for the virtual chassis link HERE. I can confirm for the EX4300 this method works as there is not documentation for the EX4300 option 1 and 2 is what I would stick with. Option 3 I would never use or could see not reason for it.
Cisco 3750 is commonly the switches I setup, HERE is the reference I use which I have applied to 2960x’s as well. Cisco Pretty much have simlar options to Juniper I for both I stick with the Port 1 SW01 to Port 2 SW02 Port 1 SW02 to Port 2 SW01