Other than more powerful coils the DOHC already has what the SOHCers upgrade up to get. DOHC coils are pretty weak.
We ran optical ignitions back in the '70s on drag race cars, they have flaws for sure and the way that 'X' system is designed? I find several things wrong with it just laying in the box. The ad they show is highly inaccurate, at least in my view.
I've run GM HEI car ignition modules on mine since the '90s using the OEM pulsers to send signal. The car coils (off a Chevy Baretta) can gap and fire reliably at .060" like a car, you will NEVER find a system sold that does that.
There is a Czech company that makes programmable modules that are jam up for helping set a custom advance curve that really fits the bigger DOHCs, they have issues with pinging in higher stressed applications due to the combustion chamber design and the carbs used.
Dyna makes a cheaper high perf setup (Dyna III) but do NOT use it! It has proven hundreds of times to be a problem maker par excellence! The Dyna 2000 is OK but expensive.
The DOHC ignition pickups are buried in engine oil unlike the SOHC, it really complicates issues, the oil heat fries parts quick.