So is type of H-bridge?
What is the maximum number of 12V electromagnets do you reckon I can run off this shield? I was hoping for at least 3-4....but I see it says you can control two DC motors with this....is that the same for electromagnets?
One H-bridge per DC-motor, one H-bridge per electromagnet, one H-bridge for every bidirectional load.
Dual motor driver boards/shields are quite common, I think there are a few quad driver boards though - you'll
have to look for them. google "quad motor driver" perhaps?
Also I was hoping to run an RGB LED strip off the same microcontroller. I've been told it uses two SPI pins and two Power pins. Is this possible? I've attached the pins list - maybe someone can help me figure out if there is enough space for these?
You have no pins for the electromagnets. That's not your list is it? For LEDs you need clock/data (they will be 12V strips
I suspect), and any pins will do (using SCLK/MOSI happens to be convenient for high-speed use)