If you follow the whole 8D methodology, in your investigations you will probably uncover systemic and process root causes which will require different corrective actions. You will also in all probability find that you can correct a situation in a few different ways.
Proposed Corrective Actions allows you to list what potential actions can be implemented (and evaluate them as you stated), and Chosen Corrective Action is where you enter what you actually did.
Preventive actions typically are systemic in nature (i.e. Update PFMEA or change Work Instruction in other areas that could have the same potential for failure, etc.).
If something is over engineered. . . it will probably be under manufactured! (Jim Eustace 1993)