forget the R18 and turbo etc.. just pull it out infavour of K20 or K24..
warranty will be voided depending on WHAT you modify, WHAT you make a warranty claim against, and WHERE you take it.
HONDA in general wants to keep you happy so you buy another honda one day so basically if you modify it, dont bother with a warranty claim on that part (or associated parts).
for example if you fit suspension, if you claim on anything to do with the wheelbearings, suspension, brakes, steering etc.. they can void it.
if you fit an exhaust system and your audio speakers die - that is OK as it is not relevant to the modifications.
I've had a customer's $45,000+ Honda warranty voided 'bumper-to-bumper'. The dealership was happy to maintain the warranty while THEY were working on the car (as they were able to claim against the warranty to incease their margins) even though it was extremely modified. Once they couldnt fix something so the owner took it to another Honda Dealership who agreed to fix the problem under warranty. The first Honda Dealership didnt like the truck coming to theirs to take it to another dealership and promptly called Honda Australia and had the bumper-to-bumper Black-Flag.
as for CF / FRP.. it is only legal to have (Fibre Reinforced Panels) fitted on vehicles that had so originally or were manufactured prior to the changes in ADR's in 1995.
so a 1972 Toyota Landcruiser may have a complete FRP body replacement and be legal.. however u cant fit a FRP door to a 1998 Landcruiser..
a 2004 Corvette may have a CF hood and fenders etc fitted as it was FRP (Fibreglass composite) from the factory.
IMO if you intend on going mental with mods on an FD civic - buy an OLD VTi that is out of warranty and dont worry about it.
Personally with the newer hondas built in Thailand - FD civic especially - i would DEFINATELY want the full warranty for a couple of years !! that's from insider knowledge yo !!
hope that helps.