Freeform Games Interest Check
In terms of a general point, I would be a little apprehensive about keeping a number of these games freeform rather than trying to include a system (even if it's a bare bones homebrew one). It does depend a bit on how active you expect the GM to be in terms of actively creating the world, piloting NPCs and leading the plot and how much you expect to leave as a sandbox, but I would certainly say that The Escaped Experiments would definitely need some scaffolding around it (even if fairly abstract) to keep players from God-modding or having very different perspectives on how dangerous the world is.
In terms of concepts, I do think the Escaped Experiments could be the most interesting from a roleplaying perspective - depending on how much you want to turn the screw, it could be anything from mutants to Prometheans to something escaped from a Drukhari lab, and I think you could pump in a lot of atmosphere and create both some very brutal but also some very tender moments if you were inclined. As mentioned before, I would probably try and apply a system to it, just so that there's a baseline that everyone is working from and you don't have a massive power discrepancy behind the player who thinks they can take their creator and the slow burn player who thinks their character is so broken they can't even hurt a fly. You'd probably also want to make this one Adult.
Behind the Veil has potential but I think it's going to require a very steady hand on the tiller and a lot of legwork from the GM to keep it going, both in terms of creating a believable world, populating it with NPCs and keeping players in check so they don't end up either undercutting each other or indeed Gordian knotting the situation and exposing everything if they lose their patience. You'd probably also want to apply some degree of system here just because especially in social games, there's a risk that a highly charismatic character can blag their way past most things and you probably want to limit that. As before, an Adult rating would probably be a good shout on this one.
The other two are somewhat less to my taste - partly, the kind of abstract 'playing with realities' really doesn't speak to me, but I also think the core gameplay loop of exploration tends to become stale pretty quickly, and the very desire to have variation across realities means that it's harder to specifically tailor characters to the setting.
But all of this is personal taste and feel free to ignore it as you see fit.