you are confusing mods with customizations. a lot of stock based roms are nothing but a theme, some build.prop tweaks (that they googled), and a few apps from the market preinstalled.
then you have something like clean rom:
[HIGH]Complete Aroma Installer! Build your own ROM the way YOU want it!
Choose Launchers: Touchwiz Launcher, Touchwiz Launcher 5x6 Layout, Apex Launcher, Nova Launcher, Trubechet
Choose File Managers: ES File Manager, Stock My Files, None
Choose Google Apps: Play Store, GMail, Google Now / Search, Maps and Streets, Talk, Voice, Play Music
Choose Samsung Apps: All Share, Kies, Media Hub, Mobile Print, S Memo, S Suggest, S Voice, Cloud, Pop Up Browser
Choose Misc Apps:AdFree, AccuWeather Widget, Polaris Office Viewer, Yahoo Widgets, VPN Client, DropBox, Android Terminal Emulator, Adobe Flash
Standard Features
De-Odexed with Performance and Battery Optimizations!
Lidroid 15 Button Toggle
Extended Reboot Menu!
No Ongoing WiFi Notification in Statusbar
Full init.d support!
Zip Align on boot!
Full Boot Animation Support![/HIGH]so it has a modified kernel, a toggle mod (for teh notifications), has power off, reboot etc in the power menu. im not sure i understand what the no ongoing wifi thing is tho. the biggest feature he offers is an aroma based install, which i can tell ya isnt a small task. its easy just very very very time consuming, my hats off to anyone that does it.
other than that its pretty much the exact stock rom you already have. i picked his rom due to the request to port it, it just happens his rom is based on making a very close to stock rom with added features so he isnt trying to overdo it with crap that many do. some of the crazier ones will have hideous themes and 17 bulletpoints to explain 3 features.
my point is those are all teh mods done to stock rom. im sure any person here could name a crapload of features of a AOSP based rom as they are fairly standard across the board.