The beautiful thing about starting a new tank is learning what you like, trying different fish, taking a chance on things that may or may not work, and discovering unexpected love of new fish. If you are starting from scratch and getting juveniles or at least younger fish; it gives you a little bit of wiggle room to try different fish until you discover what's important for you. Then you'll have your main fish that you tailor tankmates, decorations, and water parameters around. You'll have your established tankmates, and then maybe a species or two you switch out and try every once in awhile. We can give suggestions, but the fun part is discovering it for yourself! Follow some basic guidelines on tankmates, but feel free to add in a wildcard within reason.
I say this because I had my mind set on the fish I wanted and it's changed vastly since starting this tank. I got a leopard bush fish spontaneously and not only is it my favorite fish, but it thrives in my tank. I would have never gotten it with the info on it via internet because it says it doesn't do well with cichlids, but every fish is different and mine just works!
as far as bichirs, they aren't necessarily aggressive fish, they are opportunists. Anything they can fit in their mouths, be aware they may eat. Some bichirs may not touch a thing, while others will eat something larger than you realized they could handle. If you wanted to try one out, a senegal is a good start because it's a smaller species and it's mouth isn't as large as say; an ornate. It's also cheaper as well! If you find that you enjoyed your first bichir, add another or try something more advanced. If you want a bichir and you want to see more activity, you may consider looking into reedfish and get a few. They can be timid eaters, but be creative about feeding time and they'll be able to eat. I've got 3 in my tank and there is always one swimming around the tank looking like a sea serpent or water dragon. They are housed with cichlids and the cichlids don't even act like they exist. They can also go brackish so if you do decide on a puffer, they will do just fine.
As far as personable fish, most cichlid are since they are smart. It will really just come down to the fish itself. Kind of like a cat, they are domesticated to be a companion, but not every cat welcomes you when you arrive home or gives you attention unless you have food. There is one fish that is pretty special and the ultimate oddball. It's called a "freshwater dolphin fish" and it's part of the elephant nose family. Be warned, they have an incredibly high mortality rate, very difficult to find, there isn't as much info on them, and they are sensitive to chemicals, metal, and magnets. You want a pain in the arse but personable fish, that's my dream fish. Had a chance to get one once, but turned it down because it was too large. Look up "freshwater dolphin fish" or moryrus tapirus/longirostris/kanuume for pictures and videos. Frankly, most elephant nose are personable and friendly.