How Is God’s Divine Prerogative in Romans 9 Different from the Capriciousness of Allah?

Questions about how God’s divine prerogative in Romans 9 differs from the capriciousness of Allah, why we should bother with evangelism if God draws those whom he draws and no one has a choice, and the role of faith in the elect in Reformed theology if God guaranteed their salvation.   How is God’s divine prerogative shown in Romans 9 different from the capriciousness of Allah? If God already knows who goes to Heaven, and he draws those whom he draws, then why bother with evangelism since it isn’t like someone can have the choice to choose God? In Reformed theology, what’s the role of faith in the elect if God guaranteed their salvation?