I’d pick the silvers or the butterflies (the butterflies would be more comfortable in a 55). Best to go with the butterflies in this case
Silvers do best with many of them (I only have 3, if the tank wasn’t already overstocked I’d get more though).
That setup sounds good - the bichir and cat would like the lower decor and the butterflies would appreciate the floating cover.
Would Congos be better in the center? I kinda want something to fill in the middle part.