@mollylou125 I would actually suggest spending less on the PC and more on the monitor, relatively speaking. High-quality monitors aren't nearly as expensive as an entire system, but they're not cheap, and you'll be staring at this screen a lot. Spending ~$250 rather than $150 can make a massive difference in the experience of playing.
For the specs, absolutely get an IPS panel (not TN or VA). This is the highest quality in terms of color and viewing angles. I would also suggest getting one with at least 300 nits brightness, which is much better than 250 if the room has much light at all. (The difference between 300 and 350 is smaller but still noticeable; above that, it might not make a practical difference to you.) I would also strongly suggest a resolution of 2560x1440 (or 2560x1600), as the higher resolution makes everything look more crisp and clear. Finally, I'd suggest at least a 120 Hz refresh rate; above 165 or so, it makes no difference to Sims 4.
All of that doesn't come cheap, but like I said, it's very much worth the extra money considering the impact it has. You could go to 4k, especially with the hardware in the PC you're considering, but that raises the price further and doesn't necessarily give you the same improvements. I would say that playing at 1440p at 144 Hz is, for most people, clearly a better experience than playing at 4k and 60 Hz.
Beyond that, go for a brand you've heard of, and maybe look at monitors in person to see what you think of the screens. You don't need to find the exact models you're considering; just "IPS and 1440p and >100 Hz and [brand name]" will give you a good-enough idea of whether you like the brand's products.
Here's what Best Buy is offering with most of the above, aside from brightness, which you can find (listed as candela per square meter) in the specs on an individual product page:
[very long link]
You could shop elsewhere, and I could help you look elsewhere, but this should at least give you an idea of where to start.