Not sure if any custom ROM has the latest from the S4, however, some ROM developers have pulled in certain features and made them available as part of the ROM, or as user installable zip files. The ROM based features can be in some cases, selected during the ROM installation phase.
There are many TouchWiz based custom ROMs out there. A few that I'm aware of are CleanROM, Jelly Beans, and MeanBean. I personally use CleanROM as its close to stock, and the developer (Scott) and his team are great at helping beginner and advanced users alike. I read good things about the other ROMs and their developers that I listed, and believe there are likely even more good ones for North American carriers. As for the International custom ROMs, that's where my knowledge base stops.
For non-TouchWiz, there are some based on Android 4.2. Cyanogen, and Carbon are just a few.
To learn more about either custom ROM variant, here are a few links to help:
I guess what I'm looking or wanting is the latest version of TouchWiz like the S4 on my Note 2. I'm already running cleanROM 3.5 that I flashed 4 months ago and just wanting to know any new ROM running the latest version of jelly bean and TouchWiz? Anyway, I'll check out Scott's ROM and see what is out there.
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