I can tell you from experience that the schooling fish might not work out. In my 33 sorority I had 9 girls at the time with 7 Neon Tetras. While I had no problems of fin nipping I had found out that my Neons were sparring with each other which then caused stress on my girls who started to nip each other some more. I got rid of the Neons and my girls couldn't be happier!
The Cory's however are a great idea and I love my little Dwarf Cory's (Corydoras Habrosus) and even one of my Betta's; Little Blue thinks she's a cory. lol And I do have a BN Pleco as well who will be going soon.
My Pleco has actually got rather aggressive when it comes to feeding time and of course the girls try to steal her food and she whacks them with her fins and "bites" at the cory's who come too close. So just make sure you suppliment the Pleco's diet with some blanched veggie often as well as the algae wafers and whatnots.
But as far as the filters go with the AquaClear 50 since it's actually rated just for 50. I'm always iffy when filters are rated x-x like the Fluval is 20-50, it's not that it wouldn't do a good job, it just doesn't sit right with me lol. I'm weird I know. But I know the AquaClear is great, especially with it being adjustable as well. But most of the time having a strong filter in a sorority is good because it can help break up fights and chasing when it comes down to it