For the mac-n-cheese: Bring a large pot of water to a boil. Salt the water and cook the orzo until al dente, about 6 minutes; drain.
Meanwhile, heat 4 tablespoons butter in a saucepan over medium heat. Add the chopped jalapenos, the garlic and onions and cook until the jalapenos and onions are soft, 5 minutes. Add the flour and cook, stirring, for 1 minute. Add the milk and stir until the sauce thickens. Season with salt and pepper. Add the Cheddar and cream cheese and stir until melted.
Combine the orzo with the sauce and transfer to a casserole dish.
Melt the remaining 4 tablespoons butter and toss with the panko to coat. Sprinkle over the casserole and top with the sliced jalapenos and Fresno chiles.
For the guac salad: Gently toss the tomatoes, avocados, jalapenos and onions on a serving platter. Drizzle with EVOO and lime juice, season with salt and pepper and top with the cilantro.
Divide the orzo mac-n-cheese among plates and serve with the guac salad.
The orzo casserole (without the breadcrumb topping) can be covered and refrigerated for a make-ahead meal. Reheat in a moderate oven, and make the guac salad, before serving.