There are too many variables in this question. What do you want to develop? What do you want to play? What OS have you been using up until now and do you feel comfortable with it? Do you need a separation between work and home use? Since I am missing all the information, I will speak from my personal perspective, which might not be helpful for anyone else at all 😉
Would you use the same setup for work vs home?
Let me get this question out of the way first: No. For my day-time job, I have different requirements than for what I use at home. I do some freelance-work at home, but I also program for fun, so my home computer is more than capable of anything I need in those regards.
Mac or Windows, Desktop or Laptop?
For work, I need a laptop, because I am on the move a lot. For the tasks I do, I could go with any OS, though I'd probably go for a BSD or Linux. Compared to Windows, I feel like available DEs for them are way more out of the way and customizable to the way I work, which is why I prefer them.
At home, I need a desktop. I have a big setup, and I doubt a dock could handle it. Also, I don't really need to walk around with it, so a desktop it is. Currently, I am waiting for the Ryzen 3000 series release, and then I will start my desktop all over (see linked article below). In short, I will go for Gentoo Linux. At most a dual-boot with Windows, for games which do not work on Linux at all, and other (financial / learning) applications, which only work on Windows.
How would you handle gaming? Would you have a separate rig for that?
No. I game at home and my home computer needs to be able to handle everything: gaming, development, multimedia center. I also do develop games, so there is no other way. And I don't have the space for a TV, so my computer has to fill in all as a multimedia center, too.
As for the OS, I am using a lot of Steam, so Proton (Wine) does make my live rather easy. I also can handle Wine-Staging quite well, so I don't really have a problem with Linux. For anything else I might need, I still have a Windows license and a Windows installation somewhere on a SSD I can just plug in.
You will find some rigs here: