We actually have more features than the original, by quite a bit margin. What features they finally implemented came years after we had them in most cases.
There are two features we hired people to bring in and should be coming early next year now that we have developers hired. Those are editing posts without reposting, and in-line translation. Everything else we are ahead of the curve on.
As for clients, if you use a generic ActivityPub client it should work fine as we adhere to all AP standards. Just avoid mastodon specific clients and you should have the full clients features working fine.