Please try to setup CFWs on 16gb minimum. Don't even try doing it with 128 or higher.
You need the space.
Then, if you want, just FAT32 your 128+ mSD and copy everything over.
I tried setting up A9LH/Luma on my 128gb and it wouldn't format reidnand. Just... no.
So I used a 32gb and it worked fine. Then once I was done, copied over to my FAT32 128gb mSD.
But you need the space because once you're done, you gotta put games on.
So 16gb min. 64gb recommended. 128+ if you like to hoard like me. And yes, 256gb mSD works if you do it right. I know. I've done it.
But try to setup on 32gb. Best option.