When I add multiple components to a glyph, the width of the guides for the glyph is increased - am I adding components in the wrong way?
What kind of components are you adding?
I created the component by drawing it, selecting the elements, right-clicking and choosing “component from selection.” Then to insert it, I right click in that glyph and choose “add component.”
Should I be adding a diff’t type of component (smart component?)
It is automatically inserted after Component from Selection. Are you inserting it a second time?
No, I mean in a different glyph. For example, if I create a vertical component within one glyph, then create a horizontal component in another glyph, then I start a new third glyph which requires both the horizontal and vertical components. When I add the two components, the main guidelines change becoming double the width.
What you call main guidelines are usually referred to as the metrics.
What happens is that components get automatically aligned. You can disable it for an individual component through the context menu, or for the complete font in Font Info > Other Settings.