I can only speak to the MK. I'm an offsite visitor who usually looks for fastpasses there 30 days before and travels at relatively busy times. With the exception of 7DMT, you can usually get fastpasses for your next three choices. BUT... It's unusual to be able to get them at let's say 9, 10, and 11, which is often recommended and then try for more (maximizing fastpasses for the whole day). The only ones that are usually available at the very early times are attractions that have such sort lines that you wouldn't even need a fastpass, and I don't get those. Usually though three early afternoon fastpasses for popular rides are available. And after that I've usually been able to pick up another one or two for evening pretty easily. Now that I've heard about the refresh strategy many use maybe I'll try that and perhaps get more than I have in previous trips.
What we've been able to get has usually been pretty decent, giving us only one or two pretty longs lines. -- Not ideal, but not bad enough to get me to stay onsite at Disney -- I just think there are so many wonderful places to stay offsite that are an outstanding value from a quality/cost perspective, making me an offsite girl. Usually too my trips to Orlando are just four nights / three days and usually include SeaWorld, the MK, and one smaller attraction/family visit day (We have family in Orlando and in Tampa).