System using 32GB ram, BG Usage 4.8GB.
BG Programs (In Tray): Steam, OneDrive, Google Drive, MSI AB, RTSS, NVIDIA CP, Sound Blaster Command.
Scenario: HL, End Game, Hogsmeade

As you can see, my BG apps are minimal, so I think even if I had 16GB ram, the OS could probably compress BG services usage to compensate.

However, when I play a game and leave one Google Chrome HWZ tab in the background, the memory usage almost reaches 20GB. Some users have reported performance loss with 16GB RAM, which is expected since most people will have more programs running in the background than I do.
It's worth noting that the memory usage during the game may increase as I progress. Since the game is in a completed state, more unlocked 'stuff' may be running, which could be eating up the RAM. I haven't confirmed this, so your mileage may vary.
It's essential to remember that HL utilizes real-time loading for most parts of the game, so high memory usage is expected. However, it can still be further optimized.
I'm only highlighting the possibility of high memory usage being a potential bottleneck. It's also important to note that some people may run benchmarks on fresh installations instead of their personal computers. All these factors should be considered, and it's not advised to rely solely on benchmarks without thoroughly understanding the test scenario.
Isn't 4070ti overkill? I thought that was more for 4k. Any aftermarket GPUs to recommend that has good cooling?
Most 4000 cards have good cooling. The main concern is whether it can fit your case.
4070ti may be overkill, but 3070 is under-kill if you want to play games at native 1440P and High Settings. 8GB VRAM is not a lot for 1440P.
However, it's not impossible if you turn on DLSS quality to compensate.
Furthermore, if you play on a high refresh rate monitor, FPS above 60 will improve your gaming experience.
3070 @ $800 for me is a hard pill to swallow, considering it was released in 2021. Also, its performance is mediocre.
I would get a used 3070/3060TI or a 4070ti brand new. You can also wait for 4070.