Tangs are great fish but are very active and might be cramped in your tank. The suggested tank size for bristletooth tangs like the kole and Tomini is at least 75 gallons. Most other tanks require larger (and in most cases much larger) tanks. Tangs can be aggressive to fish put in the tank after the tang, so they should be the last fish stocked anyway.
Dwarf angels like the flame are nice and can work in your tank. It is hit or miss regarding whether they nip at corals. Also, they sometimes nip other fish so you want to introduce most other fish before them.
Going fish-only makes it easier to select fish as you don't have to weed out coral-eating fish. One approach is to start fish-only and then get a larger tank for the fish (say a 180) in a couple of years and keep the 55 as a reef with corals. Depending on what fish you get, you could try stocking a couple of corals (e.g., mushrooms and polyps) after you get your fish in or even while stocking.
You could have a nice tank if you add a blennie and a royal gramma or chalk bass, and then put some corals in. If everything goes well, you could consider adding a flame angel at the end.
Make sure to quarantine all of your new fish for 4-6 weeks before putting them into your dt. It is a pain, but it is the only way to have long-term success in this hobby (to paraphrase Mr Tuskfish).
