From the top:

Erianthus ravennae (recently re-named Saccharum ravennae) will exceed 10' in height in 2-3 years. Mine are 14-15'. This is the height of the plume canes. The foliage itself seldom reaches beyond 4'. Mine are 6 years or so, and are showing no sign of donut.

Miscanthus sinensis...of the varieties you mention, my favorite is 'Gracillimus.' I have a half dozen of them scattered around the property. Like every other variety of Miscanthus I've grown, they donut. It takes 3-4 years, and another 2-3 before it needs to be corrected. 'Goliath' is probably the only one which will reach 7' in your zone.

Panicum...It's unlikely any variety will reach 7' in your zone, but they are the most likely to deal well with your clay. I have grown both of the ones you listed, but now grow only 'Northwind' and 'Shenandoah.'

You probably don't have to worry too much about any of these grasses re-seeding actively in your zone. 'Gracillimus' throws off a seedling or two for me every year, but they are welcome. I watch them to see if they have desirable characteristics, and either pull them or move them.

I meant to mention this in my first reply, but forgot.

You might also consider Fargesia 'Rufa.' It's the most hardy truly clumping bamboo, and makes a great specimen.

This plant has been pruned to the round shape, but it doesn't have to be. Google it up to see other photos and information about it. It's hardy to -15ðF. I have six 3-gallon plants outside, waiting to be planted this spring...if they survived the flood.

The bamboo's leaf texture is quite nice! Thanks for suggesting it donn.

The potential height of the Saccharum ravennae plume canes will not be a problem in the area I have planned. I'm happy to hear that you haven't had the "donut" growth problem with it either.
:-)
Deb