Not the OP, but it's decently well documented that there are games out there that are having a tough time with the memory constraints of the Steam Deck's 16 GB: https://youtu.be/z94TcihZxME?t=145
Now I'll grant that maybe it's a memory leak in TLoU that would cause you to still run into issues regardless of maximum memory but 16 GB is the recommended minimum and is starting to be the minimum recommended for other newer games and that's without having a chunk set aside for VRAM, so I'd bet that you'd see decent performance gains just by increasing the available RAM without it running at higher clocks.
The list of games that want combined RAM/VRAM in excess of 16GB is steadily increasing*, if there were an easy means of getting my Steam Deck to 32 GB, I'd jump on it. I haven't had less than 32 GB in my desktop daily driver since 2017 and honestly the 64 GB I have now starts to feel anemic once you've got a VM or two running with Chrome and a game all having to contend for the same resources. Honestly, I've never felt like I had too much memory, but I have definitely felt it performance wise when I don't have enough, where things start to stutter and the frame pacing goes all to hell while things are shuffled in and out of memory. Speed isn't nothing, but there is definitely an increasing argument to be made for quantity as well.