Is it possible to move default configuration file location?

I want it on another drive besides the C: drive.

Will I have to install all of DOpus on another drive?

If you're using the private (rather than shared) configuration mode then the config will be stored in your user profile regardless of where the Opus program files are.

(I think the shared config mode also stores the config separate to the program files, probably in the Application Data folder, but I haven't double-checked the details of that.)

You can move the profile to wherever you want or, if you only want the Opus config files on another drive (which seems odd!) you could use NTFS junctions to divert just the Opus-related profile folders to somewhere else.

For help backing up or locating your config files, see this FAQ: How to back-up or locate your Opus configuration (Simple) and/or the "Advanced" version it links to.