With filtration you want more rating the better. So if it's a 30, you want about 50 or 55. And with a sorority you can still do a HOB (hang on back) filter, the flow would actually help the sorority because it will break up any fights that you have.
However if you are doing a sorority, I don't suggest a school other than cory's/1 pleco. I had a school of 7 Neon Tetras in my 33 with 9 girls. The tetras become so active amungst themselves that it was actually stressing my girls out, the same thing would happen with cherry barbs or blood fins. I'm certain that blood fins are nippy to other fish as well. So if you do decide to do a school with your girls, make sure you absolutely know they are not going to be nippy.
The ghost shrimp would probably be eaten by your girls, many think of it as a nice expensive snack lol But if you've got enough Java moss and other plants to hide in then they should be alright but I suggest getting about 10 of them. Also keep in mind that Ghost Shrimp are scavenger's and not algae eaters.
Also! QT any new girls for at LEAST 2 week's if not more. It's a hell of a lot easier to treat one girl than an entire tank. What I do is clean out their cups when I get them and let them acclimate to my tank water and scoop out a new cup of tank water when they are acclimated and put them in that cup. I then let that cup float in the big tank so they stay warm. I do this with all new girls so that they get to see each other for 2+ weeks and are less aggressive when they come out.
I change their cup water every other day so they don't get hurt from any ammonia, I keep a spare cup so that I can scoop out more tank water and put the girl into that cup right away, no acclimation needed because it's the same water (albeit less ammonia) and same temp. I empty the old cup in the sink (don't let that water into the tank because you're trying to keep disease out by doing this and that would just be putting it back in) and rinse it out to scoop more water out from the tank and change the next girl.
Also a good thing for when you have bullies because you're guaranteed to get a bully here and there. I use a clear breeder box and put the bully in that box, in the big tank. This makes it so they can see each other but not hurt each other, they can be kept like that up to 2 weeks sometimes if they're really misbehaving. I've done it for only 2 days after they calmed down and they were fine. But it's important that they always have eye sight contact so they can get used to each other's presence.
There's going to be fighting for the first two weeks or so, that's a given. They're just trying to get their pecking order establish. At this time they'll be stressed and more open for disease so I suggest doing two weekly changes on your tank at about 40-50% so they don't have a chance to get ill.
Also if you decided not to do the schooler fish you can get right up to 15-20 females in there. The more females the better because less aggression to one fish. 6 girls is the minimum girls that I would suggest and that's generally for a 10 gallon tank so you could totally fit more in there and with added filtration that's also possible.
Hope some of that helps! sorry if you already knew the parts about the sorority and the time outs