Usually vertex shader isn’t bottleneck for trees but pixel shader. Cost should be negliable. Only drawback is that you need to use “Support accurate velocity from Vertex Deformation” which need you to set:
“You must enable the new project setting ‘Accurate velocities from Vertex Deformation’. This feature causes motion vectors to be output during the base pass which has a small performance cost whether you use these materials or not. Changing this setting requires a restart of the editor.”
This fixes temporal AA trailing and will give nice motion blur for animated trees.