You don't need the ASCOM POTH anymore. It's built into the mount drivers these days. So, I'd skip that.
As for camera issues and hubs, in my experience, I've always needed one cable for each camera I've had. Now, I can have other devices on one of the cables; but I have to keep my guide camera seperate from the main camera.
Make sure the hubs are powered. They're also the devices that fail on me the most. My last purchase (after about 4 cheaper ones in a year) was a Startech industrial model (4 port) and it's lasted 2 years.