if you intend for pairs, intend to give each pair their own tank of 20-30 gallons (30 gallons if you are doing it long term would be better). What you can do, in the 55g, a group of 6 or 8 juveniles and grow them out to maturity and there's a good chance of at least one female being in that group of 6 or 8, maybe two.
At maturity thought the female will want to pair, and she will want to take and defend territory. the males will fight to show who's the strongest and whos the best choice out of the males to the female. at that point the pair should be removed in order to keep the peace in the bigger tank, the pair goes into a tank by themselves.
you can have a group of unpaired mature males only, and you can have a group of juveniles, if a female is in the mix, at maturity, it will become territorial and aggressive. you can have mature males without females, and other fish that are too big for them to eat with relative peace also, but not with a female in there.
if you want angelfish I would not do more than one male and one female in a tank under 6 ft in length, and I'm not sure a 6ft tank would work for two pairs long term, they will still cross paths. but like I said, you can have a group of males with no female and it stays mostly peaceful, maybe some squabbles over the pecking order and some pushing, but nothing crazy and territorial.
in the wild the juveniles and unpaired males will cruise around in groups, the mature males hoping for females to mature and maybe get a shot at pairing. and when females mature, they go off from these groups, stake out a spawning territory and defend it, the females do not work in a group, and make the tank tense and there's nowhere for fish to really go to get out of the females territory, and 4 ft really isn't enough space for two females to get their own spawning territory, so they will fight and try to remove the other, which won't end well for one of them.
I'm not saying you can't do it, what I am saying is, if you have the intentions on getting breeding pairs, that
breeding angelfish are not "community tank friendly", the eggs will get eaten by the pair to stop other fish from getting them first, the pair will kill other fish if they can to make the territory safe for their eggs, and other fish will eat the eggs if they can and this will cause stress on everyone which in the long run will lead to failure.
Yes, you can take 6 or 8 juveniles and grow them out and pair them off, but when they pair off, the pairs need their own tanks by themselves, and the left over males can stay in the community tank with other fish types even, and any additional females need their own tank also, or to be rehomed. You can tank females once identified and attempt to pair them with males from the community tank in order to get different types of offspring from the pairings also, this works as long as the female accepts the male as a breeding partner, if not the male needs to be removed and try another male. you might need to break a pair if the male is infertile also and try a different male to figure out if it's the male or the female with the problem.
and if you don't intend to get breeding pairs, or breed angelfish, you'd be much better off just getting a group of 6 mature males and save yourself all of that fiasco of what happens when the unidentified juveniles mature.