As far as tangs go IME - the YT and hippo are "usually" an easy pair up - again it depends on the specific ones you get, but still in a 90g those 2 would be a little tight, and that would be "it" for your larger fishes. Ideally, if your plans could afford an upgrade in a year or 2 to somthing in the 125+ range that'd still be best. Ive never hade many of the butterfly fishes (only the longnose) so others will have to fill in there.
Even in that rather big tank of mine - there are some species of tang I know to avoid, cause they are just mean as heck towards other tangs and other similar colored/shape/sized fishes. Possibly the most agressive tangs that I cannot have are the YT, sohal, and clown - as their addition would "upset" the balance of the 6 already in there. Yes I do keep a powder blue and purple together, but the ones I have get along fine with the blond naso, achillies, hippo, & orange shoulder - BUT grouping more than 2 tangs should only ever be attempted longterm in tanks in the 200+ range.
As far as the angle fishes go - there are some stunning fish out there, and several of the dwarfs are just goregous and perfect for a 90g, though keep only 1. MOST of the larger full size angles are too big for your tank - but the Navarchus (blue girdled) is borderline for your tank, but is an absolutly electric & stunning fish, if you don't mind the $180 or so to get one. Again, keep only 1 angel in a 90.