In a 150, the following Tangs are ones that should be fine:
Zebrasoma
-Yellow (get a smaller CB one)
-Purple (get a smaller CB one)
-Scopas
-Gem (more $$)
-Black Longnose (the issue is they come in large, personally not a big fan of them, but if you want one get a small one, and more $$)
Ctenochaetus
-Tomini
-Squaretail
-White Tail
-Twin-Spot
-Another orange looking one (think Cyanocheilus or cf striatus, maybe both)
Smaller Acanthurus
-Japonicus (“Powder Brown”)
-Lavender
-Convict
-Lemonpeel / Half-Black / Eibli Mimic (Pyrofeus, Chronixis)
This is for Tangs.
And I love Angelfish more, no very big (“large-large” Angels) in a 150.
Consider:
-Majestic (get a small CB one)
-Flagfin
-Goldflake (get a small CB one)
-Regal (choice to get small CB one)
-Blue-Line (wait for small CB one from Poma Labs)
-“Black Poma” / “Grey Poma”
-Singapore
-Cream / Red Sea Cream (Xanthotis- usually only available CB from Poma Labs)
-Swallowtails (Genicanthus sp- consider a pair of CB Bellus from Proaquatix, or whenever Biota offers CB Melanospilos)
-Bandit (if you can shell out $$ and get a captive bred one)
-Griffis
-Tiger (cost $$ and get a small CB one from Poma Labs)
Almost all of the Pomacanthus and Holacanthus is unsuitable for a 150. You’ll mostly be sticking to the Angels more closely related genetically to Centropyge. Any Centropyge will fit in a 150. Apolemichthys and Genicanthus are technically embedded in the “dwarf Angel” tree.
Rabbitfish. Foxfaces. And some of the other smaller species.
Smaller fish like Basslets.
If up for the challenge, Copperband Butterfly (good luck). Some of the deepwater Roaps butterflies I like them too. Burgess and Mitratus are the more common ones, though still not cheap. Declivis is rarer and might need special order. Tinker’s unavailable because Hawai’i and I have never seen Flavocoronatus in the West, and currently Guam not available for collection.
Or a CB Lemon Butterfly from Biota would actually be my first choice for a butterfly.
Not really my thing, and the females not as pretty, but some people like the Bluethroat Triggers.
Marine Betta (wait for CB one from Biota).
Wrasses (a whole world of its own for many). I see you have 4 already so maybe you might want different fish.
Do you want fewer but bigger fish, or a few bigger fish and many smaller fish?
If availability and budget allow, get aquacultured stuff.