This setup will work by just copy and pasting it into your scene.
Use the edit mode and copy the vertex to get more trees.
Works in both EEVEE and Cycles (made to look good in both, have a look at the video linked)

Default tree that comes with the node setup:

Closer view of the branches and their quality (can be improved, there is a slider for the resolution):

Mesh on the branches (There is a slider to increase quality if you need):

The wireframe for the default tree. It is made in such a way to work really efficient in the viewport and render (Has an excellent balance of faces to objects for the best speed) 

The full List of modifiers from the geometry node setup: