On this note, I'm about to get my first pc. Already gonna use my series X controller, but are there other good 3rd party controllers?
Depends how you want to go about things. For the most part unless you want something with more inputs you're better off sticking with what you have. Modern controller support for the most part just means XInput, and the farther you get away from that the less user friendly things get.
DInput still exists, but its support is varied these days AFAIK. DInput is the older style of controller input. It supported more than Xinput does, but that comes with being less standardised. That means every button has a number rather than its actual label, so when you're setting everything up its a bit messier.
There is software that can customise controller layouts, including Steam itself as well as various third party ones. They can let you get lots more out of your controller by having things like combinations and what are known as Layers, which is where an input activates a different set of input commands.
To give an example for it all, my favourite PC controller is the DS4. It's a native DInput controller, but there is software that can make it be seen as XInput for compatibility. I like DS4Windows because it's better for compatibility, but it isn't as good as SteamInput for customising inputs (making good use of the touchpad). Steam is great and recently put more focus on Sony controller compatibility, but it doesn't always work perfectly with games. Also, because it isn't a native XInput controller, compatibility with Windows is spotty and getting it to work over Bluetooth means relying on the extra software that comes with DS4Windows. The problem is that an update broke wireless function for me, and I haven't been able to get it working again since so it's wired or nothing.
An Xbox controller is going to be as plug and play as you can possibly hope for, you just might have troubles with games that pre-date Xinput.
Edit: seeing as I didn't necessarily answer your question, if a third party controller supports Xinput it's going to be fine but the more obscure it is the less compatibility any additional stuff (like back buttons) is going to have.