Instead of automatically mutating, Dynamist will build an ever growing upgrade tree for your powers.
Each power has its own upgrade tree, how it works depends on the power itself but will usually follow either a fully diverging tree or a complex web of interconnected nodes.
The number of nodes you can select depends on the form of the skill tree. For diverging trees you can always select one of the branches fully. For webs, the number of choices is proportional to the size.
Choices are not permanent, you can change your selection whenever you want. It takes a around 10 seconds for the power to reconfigure itself, during this it cannot be used actively.