It's certainly fine to set the graphics options to whatever you want. High-detail lots should be kept at 2-4 though, as higher numbers will excessively strain the game engine. (You might choose to turn down the water setting as well, since it's also quite demanding, but then again you might enjoy the look of "super water.")
It is strange that your options weren't mostly maxed out automatically, although I'm actually not sure if they reset when you edit the .sgr files after loading the game once. Still, check the ratings info right at the top of deviceconfig. You should see something like this:
=== Rating info ===
GPU: 5 GPU Memory: 4 CPU: 3 RAM: 4 CPU Speed: 2904 Threading: 3
Adjusted CPU: 3472 RAM: 16281 Adjusted RAM: 15769 Cores: 4
The first two numbers are the keys. If your GPU isn't listed as a 5, then perhaps you added it to a list of weaker Nvidia cards, rather than the uber ones? It's easy to do—the first group of Nvidia cards is classified as medium. (The ones right below are the uber cards.) The GPU Memory rating should be a 4 if you set texture memory to 1024, but check it too, just to be sure.
I doubt TS3 has any idea what RTX means, or GTX, or GT, or any of the other labels for graphics cards. They're just names in the .sgr files and don't mean anything. As long as you've ID'd your card and told the game how to rate it, TS3 doesn't really process any other data.
And yes, Steam can be annoying like that. Unchecking the box uninstalls the pack, and there's nothing to do except reinstall it from scratch. It seems a small price to pay though, considering you don't have to use Origin. By the way, in case you didn't know, you don't have to use Steam either. Once you've launched TS3 for the first time (with all packs present and accounted for), you can leave Steam out of it entirely and launch the game via TS3W.exe. You can also open the launcher directly via Sims3LauncherW.exe. (In each case, you need the version with the W.) Both files are found inside the binaries folder in the game files. Unless you changed the install location, the full path is:
Program Files (x86)\Steam\steamapps\common\The Sims 3\Game\Bin
I created desktop shortcuts for both, and Steam is never even open unless I'm checking my game library for some reason.
Finally, running TS3 at 144 Hz is more than fine. That's not a workout for a 2080; it's barely a warmup for a workout. You can always monitor GPU temps and other stats if you're worried, but the only issue would be if your card or its cooling failed outright, and I think you'd notice that.
