i've heard about polys and leaf fish being together it it being fine. For the congo tetras i've heard that everything is fine untill the polys get older. I would think congo tetras would be fine though cause most sens don't go past 10"
I have a small Senegal in my 75 community with 6 koi angels right now. No issues whatsoever. However I'm not planning on keeping him there, he just looks too much like a worm now and my Midas love worms. But him tankmates include angels cories flagtail rams rummynose tetras and a frog. He hasn't taken a shot at anyone, pretty docile tbh
IMO i think that if you're only keeping that one than you can add the smaller stuff. But if plan to keep multiple then you'd probably want to sit back do some research and look at your options. If i were you i'd give it some time to see if i'd want another.