The amount of XCH (Chia's currency) generated is a constant 64 Chia every 10 minutes. You can find this under the Chia Business Whitepaper (https://www.chia.net/assets/Chia-Business-Whitepaper-2021-02...) in the section "Post-launch Chia Emission Schedule". If you have a bigger disk that is filled with plots, then you are increasing the security of the network and thereby increasing the odds that you will win the block reward.

For example, if you had 36EiB of space filled with plots then you would be equal to the entirety of the current Netspace of the Chia Network. (https://www.chiaexplorer.com/blockchain/blocks) So you would win the reward half the time and the rest of the network would win the reward the other half of the time. (i.e. 32 XCH every 10 minutes) Of course, this is an absurd example, as to obtain that amount of space it would probably cost you on the order of $20 billion just to procure the equipment, but at least it should give you an idea about how disk size works in regards to Chia.

A bigger disk means you can store more "plots", which are the the files necessary for proof-of-storage, and thus makes it more likely that you will earn a block reward.. But in order to first generate these plots, you have to "farm" them which is a very write intensive process which is ultimately what is at focus here.

The creation of these files requires so much writing that you are basically writing as fast as your CPU can, until the drive dies.

You'd be limited by write speed.