[@Pezz570]
So onto the how much is to much. What you could do is have grades. Like a A grade is capable of destroying entire cities and armies. B grade is capable of destroying small towns. So on and so forth. A limitation you could throw on this is only a small portion of the population has this ability. The majority of the population either has limited use of non-corrupting magic or no magic.

Im not sure I understand on what you meant on the free-form structured magic system?

As for the use of corrupting and non-corrupting magic is a good idea. Corrupting magic could be magic that is able to harm or in some cases heal. And for non corrupting it can't be used for combat. just general uses.