The bandwidth control rules apply to IPs, subnets or interfaces. You can use this for controlling traffic between nodes using a wireless mode called WDS. This is specifically designed for creating outdoor PtP/PtMP links and creates a separate virtual interface for each client. I have found it dramatically increases wireless performance as well but does limit you somewhat to using Mikrotik gear for the client equipment if you want to take advantage of it. Standard clients can still connect to the access point but they will be bound to a common wireless interface which means you cannot control traffic between those nodes, so if you need such capability you might be better off sticking with your setup.

I have heard that D-Link, etc. gear use WDS for the bridge mode in their APs but as it is not a finalised standard I'm not sure if different brands are compatible with each other when using it.

I haven't implimented it on my network (yet), but have for a commercial operator who uses the same gear.

Mikrotik have excellent documentation at http://www.mikrotik.com/docs/ros/2.9/ While it is Linux-based they have a customised interface so you don't get your hands dirty. It also comes with a nice GUI interface program you can run in Windows to manage the box, which is what I normally use.