Very interesting. One thing is not clear for me: you're adding the high end with the HF channel but other information too because you're not high passing on that SSL. Is it used for overall volume of the vocal too?
The boost is so big it kind of doesn't matter. When you bring it in you only really notice a brightness.
Parallel busses can be rendered to save cpu and then all the plugins deactivated in Reaper so they have 0 hit on cpu. Is it possible in Logic?
No, that isn't that simple in logic. There is a similar work around.