WF setup question: we have 2 sign off groups

Sounds like Process Level Review. I did something like this for Atria, but it can be cleaned up to look nice on a Dashboard or something.
The issue I found was that in order to Certify, you need WFE access. This means that a reviewer can access the Questionnaire and a Certifier can access the confirmations. I had to include the WFC group within the WFE group.
WF Execution and WF Certification groups