In regards to the Real Presence:
It matters because it is the central reality of faith. It is more than material acceptance of a doctrine, more than simply grasping that Jesus is wholly there in that little round piece of bread.
The Real Presence opens up the mystery of God’s salvific action with us through Christ. It is Jesus among us without constraint of time. It is complete self gift; God condescending with humanity to the point of being the new manna in the desert. It is God asking us to lay aside our demands for big glorious signs, and give our attention to the seemingly ordinary sacrament.
Anything you can say is inadequate. Belief is response to God’s grace. I believe because Christ is the only way. And all I know is what he has shown me through the Church, personally and corporately. The Church has transmitted the words and the body down through the ages. I try to give my assent.