Collector variety not expected to be seen at a big box store. Tends to have tall open habit - should be possible to use it in situation described. Will want to be out of strong wind and hot sun, intended planting site may offer protection from this.

If it is that species it will have the characteristic leaves with hairy undersides etc.

I took a picture of it but it doesn't show the crumpled leaves with the reddish underside as vibrant as it actually is. Also, the leaves are quite grey, rather than dark green. It does look healthy though. It certainly looks like it is going to be a big boy.

Could perfectly well be R. rex. Shouldn't, however have tattered margins or leaves dropping early enough that only the most recent set is present - one branch in the center is showing this, a common cause is powdery mildew. Other frequent banes are lace bugs (I think I have sometimes mistaken their effects for mildew) and weevils. Due to the latter being prevalent you do not want to plant or store (as in potted stock waiting to be planted) rhododendrons beneath building overhangs or low branches of evergreen trees in particular as such situations really seem to bring them on.