One of the great things about custom built computers is they are often built with expandability/upgradability in mind. The big name off the shelf or online purchased computers are often only built with the bare minimum to run them as they are when built, frequently being restricted by a barely adequate power supply and very little room for expandability. The only thing that can sometimes be a disadvantage with custom built computers is the warranty. Hopefully you have a warranty or the build even allows you to use the warranties from the individual components.
Windows 7 is a great OS. Keep an eye out for that pesky W10 upgrade.
Good luck with the new computer. It's always fun learning what they can do.
Ah. Just make sure they are very specific about their overage charges and/or what may happen if you reach a certain data threshold. A lot of the "unlimited data" plans, if they still have them, will have tiny writing that says if you use more than X amount of data they "may" slow your services. I really like the "may" part. LOL.
I can get a 4G plan here for home internet, but it's too expensive, relative to what I can get, and my signal isn't all that great where I live. My closest cell tower is about two miles away, on the other side of a hill. It's enough for a cell phone, but I can't trust it enough for internet.
It's good that the guy did that for you with regard to the sneaky W110 upgrade. It sounds like a nice store.