What would be your object in trimming them? And what would the 'trimming' consist of?

Ty for ur response. im thinking bc when it continues to grow in height ( its grown 2 ft in 3 mos) that it will be too tall for trunk size and will want to start bending or fall over in windy conditions. Right now the lower half has a stake w them cause no way they can stand on their own. i have a bout 8 to 9ft willow acacia that i have to keep weights on one side to prevent it from bending to the right because has a leader that is pretty tall and catches the wind. i thot mb if i cut the top down on the young ones im speaking bout that it will continue to grow but the trunk will get thicker so wont do harm to tree in wind.

This is the tall tree that catches alot of wind. Trunk getting thicker but it likes to bend alot to the right in high wind.