I will try it. Just to double check, I've got openbox S11 HD, deleting / rescanning channels won't screw up the box?
I have no idea whether it is possible to delete all the previosuly scanned channels while making new scan in your receiver or not. This is your receiver and you have to know it better (otherwise, consult support forum of your model). In the Dreamboxes, there is an option when you make a new scan, all the available channels are erased. This is done to not duplicate the existing channels.
And in the menu I've got option for both CCcam and MgCAMD, I've things working fine with only CCCam details. If I leave them like they're and also add MgCamd details thru that file, will it be fine?
You may have as many options in the menu, as many emulators (mgcamd, cccam, etc) are available. Please be noted that for sharing, only one emulator shall be used. Read the rules of sharing and understand that if you use, say, Cccam emulator, all other emulators and settings (config files) shall be deleted. Don't "collect" all settings for all emulators in your receiver.