Don't use any of those things unless you NEED them, either to fix a problem or as a creative effect.
That being said, if you use that signal processing during the recording phase (also called "tracking"), this will free up those devices so that you can use them on other tracks during mixdown. Just remember that when you use these devices during tracking, it's commited to the recorder, no undo there, so you really need to get it sounding just right on the way in. Aside from making your processors available to you in the mix, the other reason to use something like compression during tracking is to reduce the dynamic range of a source if it's, for example, too dynamic for your recorder input, that is the quietest passages are too quiet while the loudest passages are distorting your input. Personally, I find myself doing this more when recording digitally because digital recording is very unforgiving--if you're seeing red on the meters, you're ruining your recording--whereas tape is much more forgiving, you can hit the input levels hard and the distortion and natural tape compression you get can be pleasing to the ear. I'm personally most likely to track with compression when I'm recording vocals digitally, for example, because that's a very dynamic source going into an unforgiving recorder!