A little increase in Compression Ratio (static and dynamic) from evenly deposited carbon in the combustion chamber won't hurt anything and can be a benefit, although a small benefit. Carbon fouling of injectors or plugs is another matter, though, but they do have self-cleaning attributes (fuel is an excellent solvent, and plug heat is also carbon-shedding).
I think every engine is different in the characteristic carbon deposit pattern (which is no surprise ... the heat and fuel atomization patterns are tightly dependent on Combustion Chamber shape, valve and intake / exhaust passage shape and volume, exhaust gas and intake charge velocities, valve and spark timing, piston crown configuration ... even the number and placement of spark plugs).
It would be remarkable if there weren't differences between different engine families.
There is nothing wrong with taking a look before you come to a conclusion, but that doesn't come in a bottle.
Sometimes you can learn something from taking an afternoon and cruising through a junkyard, where an engine without heads or with heads removed can be found from time to time, for examination.