1. I know that the anker hub is a more popular choice because it allows a higher current consumption thanks to its usb 3.0 design (up to 900 ma for standard specification)
I don't know which USB protocol version the protocol converter on the stick miner runs on but usb 3.0 hubs dont like running usb 1.1 devices if it is connected to a usb 2.0 host. Luckily you can force the pi to run at usb 1.1
2. For mining, RAM is not significant here
3. I personally run the pi myself for mining. You should be able to use your Mac for operating with the pi. At first run your pi to enable ssh and use your mac for remote access.
A fair warning that the pi USB can only handle so much traffic before packets start getting messed up. I would advise only run one hub with a few miners to start with.