For example, if I use Console Emulators on all tracks and buses (including Pre Master Fader) do I actually need to insert a Mix Saturator 2 as well?
If you want. There are no rules for this. There is no right or wrong way to use these.
If you feel you need to use both, then use both. If your ears tell you you need to use both or just one of them, then just use one.
Let your ears tell you what to use and at what settings to set them to.
Each song and each instrument track in each song will need different things done to it. so use your ears and do what you feel is needed. No one can tell you if you need both or just one of those things. Its all relative and personnel taste bro
Cj