I did a lot of research before my purchase so I would do the same again. Let me tell you about my findings.
As a developer you mainly work with text. You write in an IDE and observe changes (maybe live) upon hitting the run button. I assume you do not like to hit the minimize and maximize button very often. I also assume you do not like to scroll up and down very often two. Given that, my first pick is dual monitor with a dual monitor arm. Alternatively you can use an ultrawide monitor.
If you want to run VM, Docker, Android emulator etc. Then some extra ram will help you a lot.
SSD helps very much.
As far I know, Processor is not that much important for regular development works. However, you know what you might be working on.
I do not need any Graphics Card. However, If your work involves heavy graphics then go ahead and buy a Graphics Card as per your requirement.
As far OS is concerned, I use Linux Mint. You can go for Ubuntu or any of it's derivatives if you do not need to work on Graphics (Ex. Adobe Products), or you do not like to play Games. There are also some edge cases where you might miss Windows though. Moreover, if you need to develop apps for Apple then you might need a Mac.
Note:
If you are a man, and use a laptop, then you may consider not putting it on your lap. Research shows that it can eventually make you impotent. In simple terms, Your balls may boil because of the heat generated by the laptop (or, what I like to call a Balls Buster).