The first guy is Jesse Cox(youtube channel link) and he does Let's Plays. He is a great fan of Witcher, he even has a video or two, from when CD Projekt RED invited him to Poland to visit their studio(just search Poland on his channel). He did let's plays of all the titles by David Cage, which include Omikron: The Nomad Soul, Fahrenheit and Beyond: Two Souls.

Edit: I made so so many spelling mistakes!

The second person was Dodger, another youtuber(?). She's one of the other two regulars in the podcast run by Polaris, a group of high profile youtubers who do content related to games. I think some (or perhaps all?) of the other people featured are also members of that organisation. Oddly enough TotalBiscuit is a well known member of it, though (he's the third regular on the podcast along with Jesse and Dodger), and he wasn't included. Either GOG's keeping his inclusion a secret, or the Polaris connection is a coincidence.

Having watched Jesse and Totalbicuit's Terraria and Starbound videos, I strongly dispute his assertion that he wouldn't sing songs about it.

What is the game that the "be there" guy is playing?

You mean Startopia?

Crendor! I like his reviews so I am at least somewhat interested in what they end up doing with this.

Maybe, it's also the second game in the video. I guess I'll have to install it and see. (It's in my back log)

It's not the footage with the space combat, that's got to be a different game, but the one with the little people scurrying around. You can recognize it just by looking at the screenshots on the GOG page, although I won't dissuade you from installing it. It's actually a pretty nice game, one of the few real time sims even I find fun.