I'm not sure any of these are quite accurate, especially given the specific symbolism of the Eucharist.
The bread and the wine symbolize the body and blood of Christ; his birth as God in human flesh, his incarnate life as a human being, his sacrifice of death buying us all back from our inevitable end.
As we partake (whether for you this is literal or a reminder, a metaphor connecting you to the everyday realities of faith), we become a little bit of what we take in. Our bodies process and use nutrients from the bread and the wine.
But they don't remain bread and wine. They become energy, powering the creation of new cell or the repair of old ones, powering thought and movement and internal processes.
I believe it's the same for us spiritually. God does put his spirit within us, and there is an exchange between us and God that is much more like marriage or close friendship than anything else. But as we seek him more and more, as we take into ourselves his love and his holiness, his grace and his truth, we begin to change.
It isn't simply that he is within us, now. Or that we are being somehow subsumed in him. No--he doesn't want a bunch of clone versions of himself. He wants everything he is to be absorbed into everything we are, altered and reinterpreted and acted out perhaps in ways that he could not have during the specific historical period he was here among us.
The differences between us are as different--and as close to the same--as the various facets of our Eternal and Infinite God.
As St. Paul wrote to the Galatian church: "The only thing that counts is faith expressing itself through love."