You will find a diagram showing some of the metrics and terms in the FAQ Thread at the top of the support forum.
The x-height and Caps Height are calculated values based on the lower-case x, and uppercase H in your font. See this Tutorial thread: How Do You Adjust the Cap Height and x-height Lines?
See Tools, Options, Glyph for the settings to use for importing vector images to make sure that they all scale equally.
Guidelines can also help, or use the Transform toolbar to size glyphs to exact values or scale them by precise percentages.
Imported images are positioned relative to the origin, so you will have to move those with descenders, swashes, or counters that drop below the baseline.