Short answer, yes.
Long answer is that no matter what plate number you're after, you want to get the wider and deeper one. Some aren't as thick as others and therefore have less surface area per plate to exchange heat through. 5x12" by however many plates you want is the normal size you want to look for, I think. A quality normal sized one would probably suffice with as few as 20 plates.
Then there's the issue of water temps, the boiler water and domestic water. The flow rate of both waters, the overall delta T of them after they pass through the exchanger, etc. are all factors that affect the effectiveness of the plate exchanger. You could use Newton's Law of Cooling and figure it all out if you wanted, but to go back to the short answer, a 30 plate exchanger running with normal boiler temps and a decent flow rate will heat your domestic water just fine on demand. They don't thermosiphon as well as a sidearm, so eventually the water in your water heater will cool off a bit unless you leave it on to maintain the temperature. Once again, the speed at which that will happen is related to so many factors, but it will take a long while to cool.