Why not just put all fields into one list? Then hide or show fields in views to show different data in different places?

The lists have different permission levels.  People working on List A have Contribute permissions, but only Read permissions on B and vice versa.  This is a government organization so there are security controls that have to be validated.  For the List C I would like to create there will be no identifying information, just tracking metrics, so the permissions are different still.

This does sound possible. I would create list A and B. Then work on getting the values from list A to list B to update upon item change. Just set conditions to check the field values and update if changed. Once you get that working then create list C and incorporate the list C logic.

Thanks, Roger. 

I have built lists A and B -- it's the next steps I'm unsure of. I just got access to using Nintex and haven't found a tutorial even close to what I am hoping to do. I was hoping I could copy updated values from lists A and B to list C, but I don't know how to go about it. Any advice or guidance would be appreciated.

It's rather hard to communicate the exact steps and how you need to configure your workflow for your situation from a distance. But I'll take a stab at it. This example only updates date of start and date of processing from list A to list C. I didn't see any common fields from list A to list B.

1. First, you must create a workflow variable for every field you wish to update from list A.

2. Then set the variable to the value in list A field (date of start in this case).

3. Repeat step 2 for all fields you wish to update.

4. Update List C fields from respective workflow variables.

Form your requirement, I understand that possibility of the fields that can change in List A are Date of Start and Date of Processing, similarly in List B, possibility of the fields that can change are Date of Meeting, Date of Letter, Date of Reply.

1. Make sure you have Case ID column in List C (look up to List A), Date of Start, Date of Processing, Date of Meeting, Date of Reply.

2. Create a workflow on List A and set "Start automatically when a new item created" and your logic would be creating new item in List C.

3. Also select "Conditional" Start when Items are modified from workflow settings.

4. Click on "Conditional" button and select "Date of Start" - "Not Equals" -- check "Compare to Field" -- and select "Date of Start" in the below drop down, repeat the same step for "Date of Processing" field with "OR" condition.

5. When workflow triggers for conditional start, your logic would be to update the field in List C.

6. On List B, create another workflow, with conditional start only and update item in List C every time when meeting date or Letter date or Reply date changes.

Sample screenshot for Conditional Start:

Title value in the first drop down is current value, and in the second drop down contains previous title value.

If they are not equal to each other, the value is modified and so, trigger the workflow. 

And click on "Add condition" and select OR to check another column is changed.

Hope it helps.