First thing you need to tell us how many speakers you have and how they are setup. You need to provide as much info as possible.
What devices do you have connected? Blu Ray, cable or sat receiver, gaming devices, streaming device? How are they connected to your receiver?
Most of those simulated movie modes are pretty useless in my opinion (rock arena, jazz club, matrix, virtual, etc). I have a x2300 and all I ever use is Dolby Digital for watching TV, Dolby Digital plus for Netflix streaming, TrueHD and DTS-HD for Blu Ray movies, Stereo for CD's and Multi Channel Stereo or Party mode for background music. You want to use the discrete modes such as DD 5.1, DTS, TrueHD, DTS-HD as much as possible depending on your source.
I also can't access the Dolby True HD modes but it is listed in the manual. Also can't access Dolby Digital Plus Neural:X. I just think it is weird that the manual lists all of this and I can't access them
Those depend on your source material and how many speakers you have setup. They're available if your source provides the bitstreamed signal. That's why we need to know what devices you have.
Please provide some more info and then we can help you out.