These are excellent questions, and after spending almost a year now perfecting meshed parts of my network in two home/pro-consumer deployments, here's my observations:
As far as "what's the mesh throughput at hop N", if you're talking about getting out to the internet, it's approximately 1/2^n, where N is the number of hops to the root AP. The reason is simple, at each hop, airtime must be distributed between listening to a client, and transmitting that data up to the next mesh link. So, at hop 1, you approximately split 1/2 your time listening/talking to the client and 1/2 the time listening and talking to the mesh root. So at hop 2, you only have 1/2 of the bandwidth of hop 1, and you must split your time talking to the client and talking back to hop #1.
Ruckus's mesh implementation has two nice things about it:
(1) Unlike a lot of consumer WDS systems, if you are doing LAN communication, the mesh will find the shortest mesh path between two peers. For example, if you are transferring files between laptops on the same mesh AP, you get 100% of the bandwidth and none of the other mesh links are involved.
(2) Ruckus supports the concept of an "eMesh AP", where two mesh APs are wired together via ethernet. They will self-arrange into a backhaul arrangement where one AP serves as the mesh uplink, and the second AP will broadcast a new network on a new channel. This in effect gets rid of the 1/2 bandwidth loss per mesh hop, of course at the cost of adding another AP.
If you need to deploy a mesh topology that involves more than ~2 hops on N or 3-4 hops on AC, you almost certainly will benefit from using eMesh AP topologies. So, if you can run ethernet between some of the mesh nodes, or afford to add some additional APs to form mesh-eMesh pairs, you'll greatly improve the bandwidth.
At my parents place over Christmas, I noticed that they currently have a mesh topology using 7982's of Basement -> Kitchen -> Bedrooms. At the bedrooms, despite all the mesh links having 80%+ signal, there's only 30-40mbit/s of throughput. They complained the internet felt slow. I added a second 7982 to the kitchen, and wired the two APs together just a few feet from each other. So now it's Basement -> Kitchen1/Kitchen2 -> Bedrooms. This change alone boosted their bandwidth to 80mbit/s in the bedrooms.