Bob, take a look at the flowers on your Furcraea when it blooms (and share pictures here if you can). They should be quite different from the ones on an Agave.
The Mangave in bloom also looks great... I can understand why you might be disappointed, but it's still a pretty good show. If you want to pollinate them you have to collect pollen where it is mature, using a small brush maybe, and transfer that pollen to a stigma which is receptive. The male parts should mature earlier than the female parts on an average agave flower, so you would have to look lower down on the inflorescence for the female parts, which come out one per flower. But they should be really easy to tell apart.
I don't think pollinating the plant with itself will give results too different from allowing the wind to pollinate the plant without any human intervention. If it's not self fertile, the brush will not accomplish anything. But there is certainly no harm in trying.
It's a little hard to tell the scale from the pictures, but your Queen Victoria agaves may be two different forms: the smaller, offsetting one sometimes called "compacta" and the larger, solitary one which is only grown from seed. Is that last plant a different size from the others?
