A little experience with CARB and other states' emission testing. In CA, CARB was a test and and a visual inspection. A bit harder than NC, or GA where I live now. Though you could get your car to pass smog in CA, it was the visual that was dodgy. Most run-down shops were the ones to go to as they really didn't know what to look for when they open your hood, unless it's an obvious modification. However, if you are stopped by police and they suspect you have illegal mods, they will summon you to a referee where your car will be inspected a lot closer. An OBD2 car will also be plugged in to check for codes and the systems' state of readiness (among other items).

On my NA, I couldn't get the car to pass the emissions with a Link ECU and injectors, so I made all those style mods easily reversible. I had a CARB legal Jackson Racing header, but I also used a Trackdog header blanket. All the times I had that car inspected, they never lifted the blanket to check it. I knew guys with FM turbo kits in CA who removed the system and ECU every year on non-legal kits. Same with superchargers.

A lot of people, myself included, made 'illegal' CA mods, but we did them in a way that made the car easy to revert to stock every other year, as required.

In GA, it's a plug & go inspection for OBD2 cars, GA does rolling road test on OBD1 cars younger than 25 years, tailpipe emissions. My NB here in the smog-cert counties of Atlanta was a 5 minute test. They could care less what the mods are, so long as the OBD2 system checks out (no codes, state of readiness). All the states will peak for a cat with a mirror.

NC was a minor inspection (tread depth, pad depth, operating horn, all exterior lights, windshield,etc.)

I know other states are a lot more stringent with their inspections and emissions (VA, NY).

I wouldn't worry a lot about CARB legal mods unless it pertains to your immediate needs.