I am looking at Holo, ADW, and Nova Launcher, due to the fact that they are highly rated, very popular and FREE!!

If I install (and I know these are very naive questions) both of them, I can switch back and forth to test drive each, correct?
They will not have any affect on my already installed applications, correct? The most important one is SwiftKey keyboard.
I love that app. But there are others and they all will remain in place or is there a bunch of configuring I have to do once installed?
And I"m assuming that any of these will aid in the sluggish issue this thread is all about?
Thanks guys for all this help. It is really appreciated.