Hi jacquesr,
1. For game-image to line up across screens, pixels must be same size (or close). But if you have a set of monitors that line up poorly this way, there are ways to fix it:
- Reducing side-screen resolutions (as you say) to line-up with center.
- Physically shifting monitors forward/backward a bit so they are PERCEIVED to line up (a monitor's distance from the eye strongly impacts its perceived pixel size).
2. You would set CCC to Fill I think... so your center's not letterboxed & sides are filled. I have not been in CCC for awhile, someone else can answer better.
3. Strongly recommend you use MonitorMixer program to help you line up your mixed-LLL monitors. It will tell you if there is any way your screens will line up pixels for games, & also what you need to do to achieve it. You would be using the Compare function for Mixed-LLL, & you'll need to seriously increase the "Short-By Max" setting to allow your short sides through. First compare left-screen against center-screen, then right-screen against center-screen.
http://www.wsgf.org/blog/imusrt/2016/01/20/monitormixer-plp-mixed-lll-layout-finderIf you have questions, would be easiest if we knew your exact viewable sizes (diagonal).