Codex, I have been contemplating switching from Windows to Linux, due to various reasons. Manjaro, to be concrete.
How much Linux experience do you have? Any particular reason for Manjaro? I tend to suggest Ubuntu or an Ubuntu derivative for new Linux users. Ubuntu's main goal is ease-of-use. It has a large, newbie-friendly community and provides proprietary software (like drivers) out-of-the-box. Any time you run into a problem, you can easily search "Ubuntu" plus your problem and find solutions. I will admit my own bias though, and say that every machine I own is running Debian or a Debian derivative. I will say, you should make sure to know the difference between a rolling-release distro and a stable release distro. I strongly suggest the latter for a newer Linux user.
How much will my gaming hobby suffer due to such a choice? I'm asking those who have recent experience.
It mostly depends on your game choice and how much you're willing to tinker/learn. Older games that run in DosBox or ScummVM are just as easy and just as likely to work as they do on Windows. Emulating consoles is typically fine as well. Older Windows games tend to actually run better through Wine than they do on Windows 10. Newer games will likely work, but may require a bit of finagling to get working depending on what technologies the games are made with. The games that you'll most likely have problems with are newer DX12 games (they'll probably work eventually) and games that use aggressive DRM and/or client-side anti-cheats. Those are usually multiplayer shooters like Fortnite and such. I wouldn't be optimistic on those games ever working unless the companies behind them change.
The absolute easiest way to game on Linux is to use Steam. Valve is putting a lot of work into making Linux gaming as easy as possible. You flip some settings on in the Steam settings, and download and play the games. That said, there's no guarantee the games will work or work flawlessly without some tinkering. Battle Brothers works perfectly for me right out of the box. I just install and play. Underrail worked out of the box, but had some serious performance problems. I was able to resolve them by using ProtonTricks to install a specific version of .NET and now it runs flawlessly. Disco Elysium ran with some minor performance problems, but that might just be my old rig and not Linux specifically.
The next easiest way is to probably use Lutris. Lutris is a gaming client that can connect to various storefronts like Steam and GOG or install from discs. But it's main purpose is to aid in the installation and running of games. It uses community developed scripts to install and configure the game to run on your system. I use this exclusively for non-Steam games.
As far as performance, it depends on the game. Linux builds by competent developers tend to perform better on Linux rather than on Windows. Unfortunately, those kinds of developers are rather rare. A lot of the native Linux games are done by third-party porting houses and the performance won't be as good as on Windows. Games running through some compatibility layer (Wine or Proton) usually have a performance hit as well, but they can sometimes run better than on Windows if they are using Vulkan rather than DirectX and running on AMD hardware. You can find more specific benchmarking online, like at
https://flightlessmango.com.
Many games are Windows-only, and getting Wine to work with most of them can be a pain in the ass.
I'd suggest you dual boot: Windows for gaming, Linux for everything else.
You're right in that some games can be challenging to get running, especially if it's a more obscure game. Sometimes you have to mess with WineTricks or ProtonTricks, custom Proton builds and such. I wouldn't suggest it to someone who doesn't want to tinker around a bit. Dual booting is a great way to start, and ensures you can always play whatever games you want. The more familiar you get with Linux, the easier it is dealing with problems that may crop up.
On Linux, you'll need to pay a little more attention to the GPU driver.
With AMD (or Intel), you'll have no problems. It's Nvidia that can be problematic, especially on a rolling-release distro.
Dual booting can be.. sketchy. I would suggest choosing only one of the two, or doing like Catacombs and jumping between two SSDs.
That's mostly Windows being selfish and assuming it's the only OS on the drive, but yeah, separate drives can mitigate that.