As far as BIRD is concerned I believe your configuration is fine. I don't see any reasons you can't configure the machines for power efficiency as this should not make the system unstable. It will just impact how quickly BGP reconverges when there are large table changes. You could test and see how long it takes them to learn full tables from a clean slate and that would be your absolute worst case. I'm going to guess it'll be fine.
To Brandon's point, are you configuring these machines as route servers? Or will they be in the path as full routers in your network? If they're just going to be route servers, I think you should be fine. If they're going to be "in the data path" as full routers, what sort of throughput are you desiring?