Let the plant do it's thing. By over trimming you will stunt growth. Even topping will reduce the size of the main cola, but slightly increase the size of the branching colas.

I actually trim off the bottom branches as they show signs of not keeping up the growth the upper part does. Helps the top part fill out later. Bottoms like that can grow nanners too, helps control them also.

Some species will grow a better top cola than others. The more indica dominate, the larger the main cola. Sativas tend to grow what I call lollipops, like a bending grow almost.

This all equals up to find the species that grows the top you want, and keep it going.

Sensi Star top cola, trimmed