McKinley supports text as a first class object within your symbol. You don’t have to turn it into outlines (although you can do if you want to) — you can just place some text, and it’ll export correctly when you output your symbol.
Use the text tool to place text on the canvas. Just click and start typing.
Colour applies to the whole text object, you can’t have separate colours for separate character ranges. (If you want to do that, make multiple text objects!)
Use the Fill/Stroke inspector pane to set the colour as usual. You can only set a Fill colour for text.
Use the Text inspector pane to control the text formatting.
Most of the items in the Text inspector pane can be applied to individual characters within your text object. So it’s fine to have a different font or style for different parts of your string.
You can set text properties, including fonts/styles for individual character ranges, separately per weight when the ‘linked geometry’ control is set to unlinked.
McKinley will make a best effort attempt to interpolate the text between weights. This is more likely to succeed and look good if the fonts you’re going between are similar (for example, regular vs bold versions of the same font family). If you try and turn Zapfino into Wingdings, it’ll be less successful!