Concerning corner cabinets, I build mine differently than the program assumes. Ecabinets has every corner cabinets' tops, bottoms, and sides cut so that there is a variation in the surface depth (apparently so that the cabinet will fit together). I assemble mine in a different way than the program and I am not sure how to create a flat corner top.
Is there a way to restore the ledges that have been cut out of the tops or a default top that is cut like a corner but has no depth variation?
You can change many different constraints using the "Construction Settings" button or just right click in the "Cabinet Editor" and click the "construction settings". In there you will find different tabs for each part of the cabinet.
Also, in the "global settings" tab you can change under "cabinet part construction" to different construction techniques.