Question in title. I am starting to get buyer’s remorse but I absolutely love my iMac. the 5K Retina display is just amazing to work on. I just don’t know if it’s going to be powerful enough for my purposes or if I should get a PC? I’ve spent, with taxes/AppleCare and 3rd party ram (don’t upgrade ram on Apple site, that’s basically theft) $3000. I bought it at the Apple store so there wasn’t any upgradeable options and I’m OK with that anyways. I could get a LOT better hardware for $3000 building an entirely new PC. The only problem is all I have for Mac hardware is a dinky 13" Late 2016 MBP with 2.9GHz dual-core i5, 256GB SSD and 8GB RAM. I bought it for development for my previous employer when I would occasionally work remote and I don’t want to be home (basically just using vscode which is not demanding at all). But for my new venture, I don’t have much confidence the MBP will be enough. Suggestions? Thoughts? Like I said, I love the iMac, I’m just not sure the Radeon Pro 580x will be good enough for game development.
It’s massive overkill. You could very easily build a computer for $300 that would be perfectly fine for this task.
You can develop mobile 2d games on this laptop just fine. Mobile 2d game development doesn’t need a terribly powerful computer. Having higher specs (eg 16GB RAM to have more programs running at once) just means a better experience.
It’s only when you want to step into 3d games (and especially non-mobile ones) that this starts to change at all.
That’s good to hear, I didn’t realize that the MBP would be good enough alone. I guess I overestimated the requirements for 2D. I just want to do this right, as this is now my full time career fail or succeed. I appreciate the reply! 
I love my MBP, but for game dev absolutely not. I mainly use it for word and excel, and flutter dev. That’s about it.
Also, in my opinion laptops should be about lightness and portability, certainly not heavy 3d game dev, otherwise you’re hauling a monster around in your backpack.
I use a 2015 iMac for mobile game dev. It works well. The one issue is if you bought a stock configuration, I assume you have a Fusion drive? That is fine if like me you have the 2TB version as there is a 128GB SSD, so much of the time it feels like an SSD machine. If you have a 1TB Fusion, the SSD is 24GB, so a lot more time is spend accessing the hard drive.
One option is like and SSD, but a bit slower. The other is like an HDD but a bit faster. That will make a big difference for you. An option is you have the small SSD (or for people with older iMacs with an HDD) is to create a new macOS installation on an external SSD and run from that. Use something like a Samsung T5 it is not far off using an internal SSD. I have a similar set up that I will keep on Mojave for when I need to upgrade my iMac to Catalina. The Mojave installation will be booted to when I need to use old 32-bit software.