With the screen sizes increasing, in my opinion, the 3x4 layout can be too space taking and not that relevant. The size of keys is 36 dp/px in height which is a good enough size for typing.

Also, seeing that entering CVV is an important step, the user would stop, think and type to avoid typos, so give buttons with more height should not make that much of a difference.

I started with 3 rows with delete, submit and also a peek/show button. Eventually, I removed the peek button and unmasked the typed CVV.

Let me know your thoughts on this.

Although Flinto has its own quirks, it is overall a very good prototyping software.

Source files are here - https://gum.co/Kgpx