Actually by staying inside a single product line there is
Synergistic Chemical Compatibility.
This is because you're working with products all formulated by the same chemists.
So yes you can top ColorX, (a strong cleaner/wax), with M21 or any of the Meguiar's waxes. You're in essence using the ColorX as a paint cleaner.
As far as sandwiching a polish in-between the ColorX and the M21 you can certainly do this but it's not recommended by Meguiar's. The issue is that because ColorX or any wax or paint sealant will seal the surface that it will be harder for the polishing oils to do their job as the wax or paint sealant is now in the way since it's coating over the surface.
A better approach would be to use a dedicated paint cleaner or swirl and scratch remover that doesn't contain any wax or paint sealant to first prepare the paint and then apply your choice of polish and then apply your choice of wax or paint sealant.
That said, you can never 100% seal a surface and the act of pushing a creamy liquid over a waxed surface will tend to remove some of the coating which will then allow the polishing oils to do their job, so while it's not an official recommendation some people will use a cleaner/wax, follow this with a pure polish and then the wax or paint sealant of your choice.
Best thing to do would be to do a Test Spot, that is apply the product in your chosen process to one small area and check your results and if you like what you're seeing then simply duplicate this process over the entire car.
If you want to go further you could do two test spots, and compare the results of the test spots to see if there's a huge difference between the end-results and use these results to choose which approach to use.
What are you working on?
What are you trying to accomplish?
