How to get the balance of an EOA address in sway

I am curious to know about the basics of fuel network:

  1. if contract’s balance data can be stored in a sparse merle tree with with the assetsIDs as keys and balances as leaf why not making an EOA sparse merkle tree then?

  2. I am not too familiar with the basic design of the EOA on fuel → is there any recommended starting point for a better understanding of fuel network setting (starting point of repos).