Code requires that the junction box be "readily accessable. That means it is OK to be behind behind a wall if you have an access panel to get to it or above a ceiling as long as it has removable ceiling tiles. I have one behind a knee wall that i can get to on my hands and knees. Readily accessable does not necessarily translate to easy. It is just you do not want them where you would have to remove sheetrock or paneling or whatever to get to it. That would be a NEC violation anywhere in the country. A real rookie mistake. No offense.
Besides, just bring your 12/2 romex feed directly into your 4 gang box you are using to mount your switches into. Pig tail off of the feed to your 4 switches. Now all 4 of your switches are fed. Then branch out to your 4 switched lights with the four romexs. East as pie.
I concur with TR. No need for a junction box, as you'll just be making more work for yourself in the long run. The 4-gang box at Home depot is $3.74 and the specs are
here. Accessibility means that with a finished wall, you must have a removable cover plate to access the wire junction/splice. Also, be sure all pigtails extend
6" minimum to meet NEC requirements. This makes wire management and device connects easier, and even though you have more wire, it folds back on itself neater than stubby leads. Some people think they are saving money by leaving just enough wire to connect the device(s), when in fact the opposite is true. I curse homeowners who do their own wiring where I can barely attach wires to the device when changing devices, and who use shallow boxes to save pennies per box. Penny wise, pound foolish, and they should not be allowed to breed, IMHO.
Your ceiling fan should be mounted to an appropriate box-brace assembly that will support up to 50#, which accommodates most ceiling fans in residential application.
This one will handle 150# at 16" on center, or 50# when joist are on 24" centers, and is all steel construction...no plastic. It's cheap insurance to make sure the fan does no fall from its mount, and I use them in remodel applications all the time, when there is not an approved box to mount the fan/light combo on. If you are going to control the fan and light each on their own switch, you will need a length of 12-3/with ground wire for a single cable run from the switch box to the fan/light combo mounting box. This is the recommended installation for fans that are not controlled by a remote sensing device. Fan/lights with remote sensing only require the 12-2/with ground non metallic cable (Romex). If using one of these remote sensor fans, then only 3 switches are required. The downside of these remote sensing fan/light combos is losing the remote console and battery failure.
Please take no offense at this comment...if you have to ask how to do an electrical project, you should not attempt to do it without supervision from a licensed electrical contractor. Seek out one and pay a "consulting fee" if necessary to insure you are doing it properly. From what you are describing, this is a project that "most" communities would require a permit for, and the permitting process requires a drawing/schematic that is approved by the inspecting authority PRIOR to the work being done. You will get a "rough inspection" when the boxes and rough wiring are installed, and a "final inspection" at the end of the job when the inspector will test your devices to insure polarity, grounds and Ground Fault Circuit Interrupters (GFCI) where applicable (determined at drawing approval), and that you have wired the circuit into the panel properly. Electrical wiring is a Life Safety issue that should not be taken lightly. You might be surprised at how much you will save hiring a professional, vs paying one to come and redo what you have already done.
Just my 2 cents worth fro a guy who does this stuff for a living.