This is possibly one of the most confusing and frustrating things about Cubase.
Here’s the problem, you want to record a mono source, like an electric guitar. So you create a mono track and then set your mono input and hit record.
That’s fine. The problem is that when you go to add any sort of plug-in Cubase does not automatically tell the plug-in that it’s a mono track (like every other DAW on the market). So you end up with a stereo plugin on a mono track, which can cause phase issues and other problems.
As most of the plug-ins I use are stereo by default, the only solution I’ve found is to always and I mean always create a stereo track and have the input be mono. That way whatever plug-in I add will function correctly.
I honestly have no idea why they haven’t fixed this yet.