About exclusives, there's a list on Reddit, but that apparently got replaced with one on Github which is updated way more recently. There were also a few threads on here a few years ago, like this one.

The problem is it looks like gog is trying to side-load themselves into steams market which won't work because for starters Epic games is already doing that way better in what 4 years of attempt.
Second to that problem is that the steam model is incompatible with the drm free model because a wrapper is drm and as such GOG cannot 'seemlessly' transition; so when they go to try making that leap they'll find half their birthday suit torn off by the loose nail of user backlash and people either abandoning or completely jumping ship to steam solidifying the wall of steam monopsony they are trying to break into.
Meanwhile time is linear & progressive so what was their old business model will eventually run out of space because they fail to do anything substantial about the direction of the gaming industry which is set to use lock ins for multiplayer with a digital wrapper form of DRM; they will eventually run out of content that is old to sell that is drm free.

Yes they would be able to sell the entire steam catologue (if steam decides not to have timed exclusive deals), but why would anyone buy from gog an exactly the same game for more money and why would developers bother with gog contractual arrangements when they can just go stuff it steams where everyone is, GOG is gonna die away so lets not bother when we can if we don't like steams 30% cut simply use epic or sell it ourselves using steam to advertise getting it drm free from the source.

'Hello reality is knocking' without fighting for a greater impetus for DRM free gaming from developers GOG is going to find itself dead in the water; i mean it will tread it for a while, it may even set itself up with a model of 'we don't do business unless it keeps us in business' where everything is automated and priced to simply exist; but in the end it's not going anywhere waiting for a breakthrough that because of their inaction when they had the means will never come.

Yes, I am aware. Not sure about the steam “wrapper”, you mean the client, as that’s not actually drm (although it can be used for such. It is a,proprietary closed source tool you have no option but to use and submit to whatever it wants to do. GOG is dead in the water, the selling of drm has gone. Most low hanging fruit -old games for instance - are now mostly done. New gamers all do not understand a world without always on connectivity, so simply will not understand drm free or even that there was a time when everyone worldwide did not know everything about you. Hence all games are being moved into that model, even so called drm free games. GOg was never big enough to even affect that growth, it’s the proverbial piss in the sea. It’s a general worldwide systemic move.