cnMaestro currently does support selecting device-specific channels for the 2.4 Ghz and 5 Ghz radios. These options can be found in the device level Configuration tab under the "Device Overrides (Advanced)" section.
Thank you for letting us know about about adding support for channel width as well. If you need this immediately, it is possible to do using User-Defined Overrides.
This guide can assist in setting up User-Defined Overrides.