I think you can use jQuery .position()

cy.get('#element1')
  .then($el => $el.position().top)  // get 1st top value
  .then(top1 => {
    cy.get('#element2')
      .then($el => $el.position().top)  // get 2nd top value
      .then(top2 => {
        expect(top1).to.be.gt(top2)
      })
  })

Notes

Cypress use jQuery to find elements. Chaining .then($el => ... exposes the jQuery object containing the element, so now you can apply other jQuery functions that are not part of the Cypress commands.

In fact, any other Javascript functions you want.

You can also make reusable functions

const getTop = ($el) = $el.position().top;

cy.get('#element1').then(getTop)  
  .then(top1 => {
    cy.get('#element2').then(getTop)
      .then(top2 => {
        expect(top1).to.be.gt(top2)
      })
  })

You can use the cypress method next() to determine the element next to Log in button like this. next() gets the immediately following sibling of each DOM element within a set of DOM elements.

cy.get('div[type="submit"]').next().should('have.text', 'Forgot password?')