Look is similar just three times + the size. Euruptus get 8-9" and rotund. Not super active and hide a lot and live up to the catfish rep so f waste producers. They do squeak and click which if you haven't heard it, it'll drive you nuts trying to figure out what you're hearing. Mine liked to be a bully. Multipunctatus are way more active and quick like pictus and similar size. I've never kept multis so couldn't really speak to their ability to avoid being eaten.
If you want a schooling fish Denisons, Bala sharks, full grown tiger barbs(relatively cheap so a little predation wouldn't strain too much), larger rainbows like Bosemani/iridian/turquoise, pink tail chalceus. Lots of different group fish will go well with O's. With the bigger fish like Balas/denisons/chalceus I would keep it to 5-7 and the rainbows 10-12, and the tiger barbs 15 -20. All this assuming the 180, I just don't think the 4' 150 is worth it.
How I would set it up is:
2 O's
6 Balas
8 pictus
If you absolutely have to have a pleco like some do an albino bristlenose
Pool filter sand driftwood with anubias/java fern
Sorry for the long post