Thus far they sound like the same size as MTG cards: Poker size. I'm not sure how to measure the corner round and I don't have them to measure.
If the cards that you generally want to make fit a particular common style, I suggest making them in layers: A background at the appropriate resolution (with a bleed), in a template with snap guides for inserting artwork and text in the appropriate places. If things like the monster cards share the same background, you might either make a copy of the template background before adding snap guides or whatever seems appropriate to you.
A background image in, say, png format might also be useful along with notes about the size and position of boxes (basically a tool-independent template that might be used by sayyyy php function that can generate a png file of a card given a background image, an art image, and a couple text screens.
Why would I be thinking about a php function that can generate a 300 DPI png file of a particular card given the background, some metrics, and a couple arbitrary utf8 text strings in any language you feed it? … no reason in particular.
