Yes of course topping makes more colas. If you top it you get two. If you fim it, there will be 4 colas.
As far as yellowing... not everybody's plants fade. Depends on the amount of nutrients provided to and used by the plant (along with other factors)
More tops will cause the plant to be more bushy so technically if the plant is hungry it will look like more leaves are dying off. Usually speaking tho if you have a proper ph, yellowing is due to nitrogen or magnesium deficiencies. You can tell if it starts at bottom or the top of plant.