S3D allows you to use multiple processes for different print settings but I think it only works in vertical layers. In your example if you were to rotate that model so the blue part was on the print bed you could define a process to print 20% infill to a predetermined height then switch to 100% around the hole then back to 20% to top off the cube.
I'm about to upgrade from an A10M to an A10T, but I've used OctoPrint on the A10M with no issues, so I don't see why the A10T would be any different.
I'd say I'd update you soon, but shipping delays are obviously happening with what's going on in the world right now.
Just note that with any of the X-in-1-out setups, if you slice in Cura or another slicer, you can specify using the different extruders, but you won't have any color mixing without using Geeetech's software.
If you want to use multi-color printing, you'll definitely want to have purge towers (or some other purge setup) to clear out as it switches from one filament to the other, and this may take some tweaking to get set up correctly.