You'll just about always want 100% fuel with the centreline drop tank. For missiles, it's more of a question of what you prefer. I usually stick with 2*73 and 4*77, but many use 27ER/27ET combination for some extra range/rear aspect shots. The altitude should be chosen pretty much the same way as with other fighters. And for your chosen 3-4k altitude feels a bit opposite of what you said about missile effectiviness.. if someone is higher, let's say 8k, he'll have much longer range for his missiles than you have etc.. Basically what limits your altitude selection is the contrail alititude between 8-12k, and aircraft manouverability at higher altitudes. The biggest diffrence when flying the mig compared to others is the fuel. Don't use AB unless you really need to, full military power is usually more than enough to what you need to get to good missile launching parameters. If you however need to go really fast from placa A to B, climb over 12k with full AB. At that altitude the consumption is much smaller than at lower levels, and you can keep a "decent" airspeed during your flight...:)