From the rice portion to the spice level and the toppings, take your pick from the extensive range of options available on the menu to create your perfect bowl of curry rice. It was probably a bad choice to get their curry udon because it wasn't customisable (though it tastes decent), so stick to their curry rice.
As an intermediate to spicy food, I find level 3 pretty unbearable because the amount of spice in it just kick you really hard at the back of your throat and ripples the effect up to your nose. So if you want a comfortable plate of curry that's still spiced, go for the level 1 or the standard and add your desired amount of chilli powder given on the table. I would also recommend getting their katsu because that's probably the topping that's most value-for-money - huge, crispy on the outside and tender on the inside.