Basically all CPUs scale well with voltage under their stock speed (or stock boost speed).
What is different about Ryzen is how steep the curve becomes in OC. This is why there is such a noticeable "wall".
It's not like Ryzen lacks power or something, but AMD will have to work hard on the manufacturing process to clock the next generation higher.
It's difficult for your "7" to be called "expectations", as these are usually made on a basis of some analysis or experience. For now they are merely hopes.
AMD's TDP is much different to Intel's. Ryzen is in fact very power efficient, but just don't get to attached to those 65W, because it'll draw quite a bit more.
AMD Zen cores are smaller than Intel's because of inferior node. Intel core is a bit better and a bit faster, but also a bit larger. Well... there's always some cost.
Ryzen is not a server CPU (that would be Naples). Mobile Zen platform is still a mystery.
As far as mobile solutions go - Ryzen doesn't have an IGP, so there will always have to be an additional chip included (unless it's the APU you're talking about). Either way, there goes a lot of the price/performance difference.
I'm sure Zen will work well in servers, but I'm just not sure if better than the competition...
As far as HPC - we don't know. In previous I've seen arguments that this arch does not favour HPC (chiefly because of slightly poorer instruction implementation). We'll see how that goes.