@lsim2fan If your goal is to play TS4 on the highest graphics settings, the two features that you need to pay attention to are the processor and the graphics card. (Other hardware matters too, but you'll get enough RAM and storage in almost any model that fits the other criteria.) There are plenty of good processors that can handle TS4; the critical decision is the graphics card.
Right now, an Nvidia 1050 ti can run all TS4 packs on the highest settings, but that may not always be the case as the game continues to develop. A 1060 3 GB is stronger, and it may or may not be quite enough for ulltra settings once TS4 is done. A 1060 6 GB is a little bit stronger still and will certainly be good enough.
The issue is that the 1060 is being phased out; one site I checked is sold out of it entirely. The newer 1650 is not as strong, and the 1660 ti is stronger but also significantly more expensive, at least right now, a couple of months after its release. So for what you want, you may be kind of caught in the middle.
I checked prices on four different sites, and the cheapest laptop with a 1060 6 GB, at least of the reliable brands, is $800. This is a Dell, which I wouldn't usually recommend because of the price, but the products are well-made enough. This particular model has a small solid state drive that will make Windows boot quickly, but it's too small to hold TS4; you'd need to install on the larger, slower mechanical drive. This wouldn't make a difference to how the game runs; I'm mentioning it in case you have other plans for this computer and would like a faster hard drive. But this computer would run TS4 very well.
https://www.amazon.com/Dell-Gaming-Laptop-G5587-5859BLK-PUS-Anti-Glare/dp/B07CD3MRZD
I didn't see any other models with a 1060 6 GB for under $900.
If you'd like to save some money, this Asus is $700 and comes with a 1060 3 GB, which again is more than enough for TS4 now but might not quite be in a couple of years. This laptop has the same good processor as the one above. Its drawback is that it has only a single 256 GB SSD, which would be enough for TS4 but not much else. However, I checked the manual on Asus's official site, and it's very easy to add a second hard drive. A quality 1 TB HDD might cost you $40-50, a 1 TB SSD (in case you're really into fast reads and writes) would be around $110.
https://www.newegg.com/p/N82E16834235081?Item=N82E16834235081
There are lots of models that come with an Nvidia 1050 ti, and if you're okay with that card, I can find a few that look good. But it's unlikely that the 1050 ti will be able to run TS4 on ultra by the time the last packs are released. It will still be miles ahead of your MacBook Air, for what that's worth.
If you have any questions, or you'd like different options, please feel free to ask.
