Sorry for the late reply.
I'm just browsing again after a while and came across this.
Sims 3 cannot address more than about 4GB of video memory, and 4GB of system side memory.
Since it doesn't hard-cap it, setting it to 2GB is plenty as that is the most it looks for when configuring.
For the CPU, it's the highest level (uber) for any modern CPU unless you have a 2 Core laptop CPU. When adjusting settings, generally just turning down active lots is more than enough to save CPU time. However, on particularly weak computers you will need to have the settings limit the number of sims that can be active in the world.
You will want to run the game in XP SP3 or Windows Server 2013 Compatibility mode. This provides the best compatibility.
As of runtimes make sure you install .Net Framework 3.5 This basically is just the libraries for legacy programs like the launcher (seriously, EA, update that launcher to run the game's internal Mono subsystem that ships with the game.) You may also need to install Microsoft Visual C++ runtime, but this is far more likely to be already installed.
I really wish EA would remaster Sims 3 with a 64bit binary and a new launcher. This would save us having to worry about this compatibility stuff, and would also let it run out of box on Steam Deck which currently requires all sorts of hacks to run it.
