Tiger barbs keep the aggression to themselves if you have a decent number of them - I have 10 and they dont even fight amonhgst themselves anymore now that an order has been established among themselves.
As for the Neons - id suggest doubling that number (at leasat double) youll enjoy them more in numbers, theyll feel safer and thus be out n about more often - whilst we knowthe gouramis wont hurt them, they dont know this - uo the numbers, a tabnk athat size will take alot of fish - you know what ny stock level is and all is cool