Guitars, bass guitars are always mono, if you want a fatter sound or use stereo efxs ( i.e. modulation fxs as chorus, phaser...)
try to duplicate original tracks on your daw and work them. Then, blend with original or in the way you like it.
Always have an eye on phase issues by listening on mono and stereo. If some parts of the sound are lost in the guitar submix you are building , then correct phases.
edit: sorry for the bump of old question, but this is an interesting ask.