As I said I am still learning about the Angels. My Aunt kept them for years.
When I saw these Koi Angels I knew my mom would love them so I got a few in case we could get up to a breeding pair.
I think it will depend on the personality to some degree. Also if there is a pair they might get cranky/territorial during breeding and eggs.
I think there is debate on if one fish would be happy solo, I have read that some are fine as an only fish. I also think there are lots of variables.
Long ago I got an Angel and he was an only in a 29G tank - I didn't know it was too small for him and the community fish and he got nasty with all the fish so I took him to the store for a better home match.
So it could have been the crowded/too small tank, lack of cover/water parameters not good, wanted a mate, had a nasty disposition...lol
I think it will depend somewhat on the fish. I also have read that having him in the tank with the tankmates will be a good thing, as they are always there as he is growing up. But not a guarantee.
From what I understand other than Wild angels, or first generation fish, the fish store or home bred fish will be fine. All relatively the same care and behavior and size for commonly available varieties.