Because the ITB & IWB have been built using the Sapling addon and the nodes that come shipped with Blender, it should work in any version of Blender that has these nodes, though I would always recommend anything above 2.8 to be certain as this is the version it was built in. All of the Infinite Builders are fairly GPU intensive, on an RTX 2060 with 8gb ram it's very smooth in the viewport, but on a mac with a 12-year old ATI HD5770, the updates are somewhat slower, but still workable.

The only limitation you will find is how many subdivisions your system can handle and render for the Displacement Effects. It was built on an i7 8th Gen 8750H, an NVIDIA RTX 2060 with 16Gb ram.

The manual comes in the form of a pdf file which will be with the ITB Blender file in the downloads. The preview is below. It's very simple to follow with clear visual examples. You can also download the ITB Tree Catalogue which details the render requirements and face count of all of the trees.

I will also be recording a tutorial series soon.