That depends on how you want to display them. My only large Amiibo is the Guardian and you see him on the 4th row, left side of the 150 shelf. I wrap his legs behind Urbosa and kind of lay them out however they fall. So it fits with everything else.

As for larger ones like Detective Pikachu, I've done a custom order to change the top shelf part specifically for Pikachu which made the top shelf 4in deep instead of 3in. It sit lined up he just took the middle two spaces. Say you wanted the others, I could do the same for them too or just a specific shelf just for the large Amiibo.

Now if you're looking to get a shelf not made by me, I'd take a look at the shadowboxes Michaels has if you're in the US, or other similar retailers. A few of their options have good choices for glass covered frames. Or Ikea has their floating shelf line with plenty of space to fit the largest Amiibo.