Either way though, I will need the BMD Talkback Converter to make it all link up correct?
Not necessarily, that was one of the main reasons why I thought a third-party solution may be better for reliability. If you use Blackmagic's intercom through the ATEM, you don't necessarily need the Talkback Converter if the fiber converters you get keep all 16 channels of SDI audio. Blackmagic's intercom uses channels 15 and 16 of SDI embedded audio to do 2-way intercom, one channel for talk and the other for listen.
Any other brands of Fiber converters that you know are reliable besides the one you linked above as a possibility.
Some good brands to look into for fiber solutions are AJA, Telecast (Rattler), Thor, Cobalt, Lynx Technik, and MultiDyne.
As for cameras, i'm going to search the community for recommendations and as to what the difference are. But...if you have a link or suggestion that would be helpful as well.
I have a list of cameras I recommend and there have already been some good discussions in the community about cameras as well. But the community is only a couple weeks old, so there's not a ton yet.
Here's my list of camera recommendations: The Best Cameras For Live Streaming