Versions

This plugin is free to use in lite version.

The Pro version is $39 and $15/year for updates.

The lite version will allow you to :

Install themes from the store or any git repository (composer, github, local filesystem etc)
Define your own themes that can extend each other
Choose which theme will be used for which site, language, viewport or url path according to a set of rules.
Compile scss files

The Pro version will allow you to :

Define regions in your themes
Assign blocks to the themes regions
Define your own blocks
Define your own view modes for each entry types/category groups/global sets/tag groups/volumes/users layouts
Choose how your fields and assets are displayed on the front end depending on their view modes and options
Define your own fields and assets displayers
Use a templating cascading system that allows bespoke rendering
Eager load fields automatically
Use several caching layers for faster rendering

What it doesn't allow you to do :

Themes