Other things, it's really case by case. The mistake a lot of people make (including myself) is to just slap everything in a stereo track and call it even; but what that ends up making is a big mess of your stereo field and a surprisingly narrower perceived width. read more
Mono source = mono track. Stereo SOURCE = stereo track. And take note: choose according to the source, NOT the end result! (I’ll explain this in a bit) TL;DR: finished stereo tracks, stereo samples, and stereo keyboards and audio devices that use one stereo cable go to stereo tracks. Everything else go to mono tracks. read more
You can create a stereo doubling within a single Channel Strip by using a Delay plug-in—specifically a mono-in, stereo-out version of the included Stereo Delay plug-in. In the last insert slot in a mono channel, choose Delay -> Stereo Delay (Mono->Stereo) from the plug-in insert pop-up. read more