Deanna I can't answer all your questions but here is what little I know. I have 7 different butterfly bushes, none of the compact variety. Butterflies go to each of them at one time or another since all do not flower at the same time. I have not watched if they use one more than the other. Something to consider is buying some this year instead of waiting. Many garden centers are or will soon be running clearance sales and you would be able to purchase one or more at a great savings. If you do just place some mulch to protect them over winter. Each fall I cut the branches back to about six inches above the ground while others do this in spring because of the winter interest the branches create. Lastly consider planting some butterfly attracting flowers around your butterfly bushes. Hope this helps..

I've never had any luck with compact varieties, they won't grow for me at all, just shrivel up and die if I don't dig them up first.
I've got a White Profusion that I've had for years that continues to make beautiful blooms all year long. If it gets too big, I just prune it, and I keep the spent flowers cut to keep it blooming.
I've also got an Ellen's Blue that's very impressive - I've only had it a couple of years, but so far it looks like a winner, and I love the color of the blooms.
Black Knight's Grape Nehi-colored flowers are beautiful, but no matter how much I fertilize or prune mine, it's still leggy with few blooms. I may dig this one up and plant another Ellen's Blue - blue (and white) flowers blend in with any other flower color, which is good, too.
Sherry

Try the Nanho purple varieties - they're great.

The butterfly bushes that get the most attention in my garden are, Honeycomb, Bicolor, Red, and Black Knight. I am learning the importance of taking cuttings and starting them when I trim them back in the spring. Buddleias can easily croak without any indication of what the problem is. Also, by cutting them back in the spring, they won't get too tall over the summer. They are very easy to start from cuttings.

Also, you will need to dead head them to keep them in good shape and blooming.

My buddleias are surrounded by all kinds of host plants and other nectar plants. I think this is key to bringing the BFs in. The monarchs nectar on the Buddleia and then lay their eggs on the Swamp milkweed and A currassivica that are growing next to it.