Hi and welcome to the forums.
We have a ton of threads on this stuff. If you have an opportunity, give our search feature a try.
As far as your specific questions, adding a CAI doesn't do much other than create sound. These add minimal horsepower and mostly at the top of the rev range. You'd be better off replacing the OEM filter with something like a denim Greenfilter or an AEM Dryflow. The Hellcat airbox, to my knowledge, only works for 2015 and up.
For exhaust there are tons of youtube clips. Search "mid muffler delete" and see if that's more of the sound you're looking for. It's very inexpensive and can be done by a local muffler shop in less than an hour.
2016 Charger R/T Scat Pack
2014 Charger R/T Blacktop
2011 Toyota FJ Cruiser
I can teach it to you but I can't understand it for you.