The only place it's really going to affect you is where you've got two switches with the diverging routes together like in the picture Arlaghan just showed you. Unless you want your tracks spaced 1-1/8" apart (which I believe is what the Peco Medium Radius will land you at if you connect them directly together with no straight section in between), then you'll need to put a section of straight track between them to get your desired centerline to centerline spacing.
Where did you download XtrkCAD from??
Where did you download XtrkCAD from??