Welcome to stratland.. of course a lot has to do with style of music and the rest of the signal chain, but there are quite a few generalities.
Start with the neck pick up. It easily provides a warm driving tone for lead and a relatively thick rhythm sound that is still significantly more articulate than a humbucker on a 24.75 guitar. It's my favorite crunched position on a strat.
Position four is your first "quack" position... As you noted, it can be less powerful but if adjusted correctly, it provides the quacky somewhat nasal cutting tone that can cut through a mix on lead. And for the same reason it is my 2nd favorite rhythm position because one three and five are louder for soloing. This is my second favorite crunched position on a strat.
For me, most of the time the middle pickups purpose is to create that quack between the middle and the neck and the middle in the bridge and positions two and four. It can be a somewhat boring pickup at times by itself. It tends to be very clean, with an almost acoustic sound and I have used the middle pickup to get a clean chorus acoustic kind of tone many times.
But the middle pickup can also be very useful. I have one strat where it does provide great quack in two and four, however it also acts as a good lead and rhythm pickup that falls directly in between one and five. So it's a bit of a trade-off but you can get a very good three position with the right pup.
Two, once again is quacky, the bright version of quack in number four and it's famous for clean leads with knopfler Clapton Albert Lee, , pretty much anyone who loves strats. It's my primary clean rhythm position, because you can really dig it hard without overloading.
Crunch with two is pretty biting, which can be very useful to cut through or to create stab rhythms.
The bridge pickup on a strat can also be useless at times. Of course it is creating the quack in the second position, so it is crucial. But on many strats it is the least useful pickup by itself. It can be bright and not balanced with the rest of the set.
However, once again I have a strat that has a wonderful one position and still quacks as well. And just to give kudos to that strat, it really does well with light crunch getting an almost PAF like AC/DC tone.
As far as EQ, I play lots of different styles with lots of different EQs so not sure I can connect any to a specific position.