Well, S-Voice isn't that great. Why not use Google Voice, which is probably more what you're looking for. I just wrote a whole guide up on it:
http://forums.androidcentral.com/gen...oogle-now.html
To access it on your S4, you can use the Google search widget (or app) or long press your home key and choose "Google"
Camera: I don't have an S4, but I have an S3 and I am assuming the camera apps are the same (or roughly the same). The camera is sortof customizable. If you long press one of the 5 buttons on the left, you can customize what shows up there by dragging and dropping another button there. It's possible you just don't have the flash option easily accessible (although if you don't, it's always under the settings/gear icon). Panorama is also there under Settings -> Shooting mode.
The file option is like a file manager. It's not for creating documents. S-Memo is really for just taking some quick notes (which you could use any note taking app, such as EverNote for). If you want to actually create documents, you'll probably want to use something like Google Drive, which in addition to be a cloud storage solutions (for documents, files, etc), allows you to create documents:
https://forums.androidcentral.com/e?...token=BCbaPetW
If you want to password protect a document, I don't think Google Drive will let you (you should have your phone locked with a pin code). However, you could use EverNote, which will allow you to password protect individual notes/documents.
https://forums.androidcentral.com/e?...token=YAxrqbF7
For wiping or locating a phone, there are a lot of options. I personally use Cerberus, which lets you locate the phone, take a photo, record audio, sound an alarm, etc.
https://forums.androidcentral.com/e?...token=ADuXLSlr
Lookout is another option:
https://forums.androidcentral.com/e?...token=mOTq9AbC
I hope that helps.