The Last of Us Part 2: The clip shown in the presentation operates at the same native 1440p rendering resolution as the performance mode in the standard PS5 game. However, PSSR is used instead of a more basic upscale, giving a presentation comparable with native 4K. Why didn't Naughty Dog increase resolution? Well, PSSR has a computational cost on its own, while various elements such as post-processing are likely running at native 4K resolution.
Ratchet and Clank: Rift Apart: The footage looks to show much the same visual feature set as the existing Performance RT mode. However, internally rendering resolution varies between 1440p and 1800p, with a pass of PSSR to deliver a 4K output.
Alan Wake 2: There isn't much video here, but there are clearly 30fps and 60fps modes, targeting 1260p and 864p respectively. Again, as the footage was easily countable, we're confident this is using PSSR. Screen-space reflections are evident in the 60fps mode, but they are not in 30fps, suggesting RT may be in play.
Gran Turismo 7: Adding quarter res (1080p) ray-traced reflections in gameplay has a hit on GPU performance, so internal resolution drops in the clips seen to 1188p and - again - PSSR upscaling is used for a 4K output.
In terms of the rest of the presentation, we counted Assassin's Creed Shadows at 864p, targeting 60 frames per second, while there are no signs at all of PSSR present in the upgraded Horizon Forbidden West. I'm reminded of Guerrilla rolling its own checkerboard solution for PS4 Pro, as opposed to using the hardware.
Putting aside the caveat that these games may not be final - and that the upgrades may be lower resource retrofit patches as opposed to from-the-ground-up PS5 Pro implementations, it's important to understand exactly what Mark Cerny's 'Big Three' enhancements are supposed to achieve. PS5 Pro receives extra GPU horsepower, enhanced ray tracing capabilities and machine learning capabilities. The idea is for the Big Three to work in tandem, delivering superior quality visuals from a more holistic standpoint. Internal resolution is only one element of overall image quality and PSSR is already showing some promise, delivering results that diminish the importance of the base pixel count.