I'd skip the boese. They will eat the Amano and your harlies. They get 6 inches each over the years, so definitely too large for this length of tank.
BUT if you like rainbows, why not consider a small species that *would* work with your list there, such as Melanotaenia sahulensis or Melanotaenia praecox? Personally, Sahulensis are healthier fish and are small but lovely. If you can get them, they're a great option. (Sometimes sold as maccullochi as well, but true maccullochi are also a great option!)
These would at the very least NOT eat your harlies. Can't promise on shrimp, even Amano, but you can attempt and see since they're a smaller rainbow species.
They'd work with the rest of your stock and not overstock the tank either.
Alternatively can't go wrong with pseudomugil gertrudae, they'd be great with both the shrimp and harlies, though they're small, like harlies. But they're good "rainbow" options too
