I'll strongly agree with the "vastly differing opinions" conclusion.
I can tell you for sure that the Eibach lowering springs common to the BG chassis and ZX2 S/R are not what you want. If they were linear springs at the higher of their two rates they might be just right, but as progressives I didn't like them at all (on crappy roads too for that matter).
Locally the consensus seems to be that stock or slightly stiffer than stock is what works well.
My ZX-2 currently has the Ford Motorsports struts with stock ZX-2 springs. So far I like the setup. It's worked well so far for a mud fest rallyx, grass/dirt/hayfield rallyx, and a couple of autox events.
A lot of the subaru guys around here go to sti pink springs which are stiffer than stock but not outrageous.
I don't know how results usually shake out on your courses, but it's not unusual in OH or MI for scca stock class cars (non adjustable dampers with stock springs) to take first overall.
As for the yumps, I'd be thinking about your bumpstops. Replacing the stockers which are probably super hard would be a good idea but I don't know if you'd want to go with stock replacements, stiffer, or softer ones.
In the motoiq frankenmiata article they discuss using some modern foam bumpstops, same concept as the flyin miata/ FCM miata bumpstop revolution. I though about trying something along these lines to get a bit more compression travel but didn't get around to it before I swapped my springs out. Luckily the BG chassis has a decent amount of travel so hitting the bumpstops hasn't been an issue for me. It might be for you with the yumps.