If a commonly used os/form factor is not on the list just add it in the comments. Also note what you use each for if possible (e.g, music production, video editing, web-browsing, writing, email).
A 'PC' style computer (apart from being a tautology) is a separate box + screen...you get the idea.
Got a phablet? let's say a phone stops being a phone and starts being a tablet when the screen size exceeds 6.5"
If you have a laptop/tablet convertible then select both categories.