You don’t need to include “configFileParameters” when pushing templates using cnMaestro, those settings are for directly importing configuration on devices. cnMaestro will tell the device to automatically reboot if required.
jsonlint.com is what I use and the “pro” version linked there has a nice diff tool.
There’s others that have visualizers that display the JSON as form you can edit for those not as comfortable editing JSON directly. I found the below site for that but I’m sure posters here have other great suggestions.