1, seems weird, wouldnt you just spawn the coins on death? if so, then the number of enemies spawned shouldnt matter.
UNLESS, you are “spawning” them by placing them in the world, and using an exposed variable to set a value for the number of coins dropped.
2, Yes, there are random number nodes, clamp it to a certain range, feed it into a for loop, the for loop has a max loop count of (random number) each time the loop passes, it spawns another coin, until it hits the loop count.