For #1, I would consider using wired connections on both ends. Even inside my home, I sometimes get the dreaded buffering on my Roku. I'm hoping for an enhancement that allows you to hide the buffering message in order to avoid getting questions about what it means. Not holding my breath for that. Anyway, the important thing on your end is the upload speed and on the other end is download speed. You will want a solid 10MBps and may need more depending on the load in your house. If your router has the capability, you may want also want to read up on the Quality of Service (QoS) features. You may be able to give priority to those particular devices on your network.
For #2, I have the Roku and it's pretty good. My bitrate tops out around 5200-something with the SB 500. It's basically 720p quality even though all connections support up to 1080p. Again, I would opt for something with a wired connection.