Is any usable content actually locked behind Amiibo cards?

So I used my Harriet card that came with my game and was a bit surprised to see there were no requirements for her home and best I could tell she didn't come with any extra items. And aside from the "special" characters, all the amiibo card characters do seem to be ingame and while each character unlocks items to use, apparently more than one animal can unlock the same stuff as well (I haven't seen repeats myself, but I've been told this).

So is any content, usable in a normal design (so, not people), actually locked behind amiibo cards or is it just a way to make sure you get to make a home for someone?

Solution 1:

No it's only "specials" like Tom Nook and Sahara and Timmy Nook etc etc

All other characters can be found in game through playing a lot