Only thing with multiple Sevs is your going to be a situation kinda like mine.
I have multiple Rotkeils (growing up to form a breeding pair)
Even at this stage now where the biggest 2 are around 3.5-4" (both female) and the rest from 2.5" to 1" dithers are getting battered.
I tried 20 Rummynose tetras, all of them got eaten, just trying Odessa barbs now and they are swimming around with tails torn to shreds.
The Bolivian Rams get beaten up if they go to mid levels and have few battle scars, the only things that are truley safe are my plecs...and they hate eachother... haha.
Sevs are not nasty fish, but the are displaying dominance/ territorial behavior, possibly showing off to each other also for possible mates.
So if you are going to have multiple Sevs and you don't want the nasty breeding behavior, get 2 females.
Males will fight like hell but females tend to be the more agressive fish in my (vast) experience (with Sevs).