The dual pack comes with installation directions, a cable splitter if needed and should work. The devices use the cable to send/receive information and co-exists with cable/internet information. You will need a router that has an Ethernet connection where your cable is connected to your modem. The second Moca will be connected at your guest house and can will connect you Ethernet device through the MoCA.
Yes, it will work for gaming and streaming. I use it with my Xbox for gaming and watching videos. Works much better than when the Xbox was connected through wireless.